BASELINE: Update chromium to 44.0.2403.47

Change-Id: Ie056fedba95cf5e5c76b30c4b2c80fca4764aa2f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

1 files changed, 394 insertions, 120 deletions

diff --git a/chromium/ui/events/platform/x11/x11_hotplug_event_handler.cc b/chromium/ui/events/platform/x11/x11_hotplug_event_handler.cc
index 3ce944efc3e..20428977e5d 100644
--- a/chromium/ui/events/platform/x11/x11_hotplug_event_handler.cc
+++ b/chromium/ui/events/platform/x11/x11_hotplug_event_handler.cc
@@ -4,6 +4,7 @@
 
 #include "ui/events/platform/x11/x11_hotplug_event_handler.h"
 
+#include <X11/Xatom.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
 
@@ -13,11 +14,17 @@
 #include <string>
 #include <vector>
 
+#include "base/bind.h"
 #include "base/command_line.h"
+#include "base/location.h"
 #include "base/logging.h"
 #include "base/process/launch.h"
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string_util.h"
 #include "base/sys_info.h"
+#include "base/thread_task_runner_handle.h"
+#include "base/threading/worker_pool.h"
+#include "ui/events/devices/device_data_manager.h"
 #include "ui/events/devices/device_hotplug_event_observer.h"
 #include "ui/events/devices/device_util_linux.h"
 #include "ui/events/devices/input_device.h"
@@ -25,65 +32,190 @@
 #include "ui/events/devices/touchscreen_device.h"
 #include "ui/gfx/x/x11_types.h"
 
+#ifndef XI_PROP_PRODUCT_ID
+#define XI_PROP_PRODUCT_ID "Device Product ID"
+#endif
+
 namespace ui {
 
 namespace {
 
-// The name of the xinput device corresponding to the AT internal keyboard.
-const char kATKeyboardName[] = "AT Translated Set 2 keyboard";
+// Names of all known internal devices that should not be considered as
+// keyboards.
+// TODO(rsadam@): Identify these devices using udev rules. (Crbug.com/420728.)
+const char* kKnownInvalidKeyboardDeviceNames[] = {"Power Button",
+                                                  "Sleep Button",
+                                                  "Video Bus",
+                                                  "gpio-keys.5",
+                                                  "gpio-keys.12",
+                                                  "ROCKCHIP-I2S Headset Jack"};
 
-// The prefix of xinput devices corresponding to CrOS EC internal keyboards.
-const char kCrosEcKeyboardPrefix[] = "cros-ec";
+const char* kCachedAtomList[] = {
+  "Abs MT Position X",
+  "Abs MT Position Y",
+  XI_KEYBOARD,
+  XI_MOUSE,
+  XI_TOUCHPAD,
+  XI_TOUCHSCREEN,
+  XI_PROP_PRODUCT_ID,
+  NULL,
+};
 
-// Returns true if |name| is the name of a known keyboard device. Note, this may
-// return false negatives.
-bool IsKnownKeyboard(const std::string& name) {
-  std::string lower = base::StringToLowerASCII(name);
-  return lower.find("keyboard") != std::string::npos;
-}
+enum DeviceType {
+  DEVICE_TYPE_KEYBOARD,
+  DEVICE_TYPE_MOUSE,
+  DEVICE_TYPE_TOUCHPAD,
+  DEVICE_TYPE_TOUCHSCREEN,
+  DEVICE_TYPE_OTHER
+};
+
+typedef base::Callback<void(const std::vector<KeyboardDevice>&)>
+    KeyboardDeviceCallback;
+
+typedef base::Callback<void(const std::vector<TouchscreenDevice>&)>
+    TouchscreenDeviceCallback;
+
+typedef base::Callback<void(const std::vector<InputDevice>&)>
+    InputDeviceCallback;
+
+// Used for updating the state on the UI thread once device information is
+// parsed on helper threads.
+struct UiCallbacks {
+  KeyboardDeviceCallback keyboard_callback;
+  TouchscreenDeviceCallback touchscreen_callback;
+  InputDeviceCallback mouse_callback;
+  InputDeviceCallback touchpad_callback;
+};
+
+// Stores a copy of the XIValuatorClassInfo values so X11 device processing can
+// happen on a worker thread. This is needed since X11 structs are not copyable.
+struct ValuatorClassInfo {
+  ValuatorClassInfo(const XIValuatorClassInfo& info)
+      : label(info.label),
+        max(info.max),
+        min(info.min),
+        mode(info.mode),
+        number(info.number) {}
+
+  Atom label;
+  double max;
+  double min;
+  int mode;
+  int number;
+};
+
+// Stores a copy of the XITouchClassInfo values so X11 device processing can
+// happen on a worker thread. This is needed since X11 structs are not copyable.
+struct TouchClassInfo {
+  TouchClassInfo() : mode(0), num_touches(0) {}
+
+  explicit TouchClassInfo(const XITouchClassInfo& info)
+      : mode(info.mode), num_touches(info.num_touches) {}
+
+  int mode;
+  int num_touches;
+};
+
+struct DeviceInfo {
+  DeviceInfo(const XIDeviceInfo& device,
+             DeviceType type,
+             const base::FilePath& path,
+             uint16_t vendor,
+             uint16_t product)
+      : id(device.deviceid),
+        name(device.name),
+        vendor_id(vendor),
+        product_id(product),
+        use(device.use),
+        type(type),
+        path(path) {
+    for (int i = 0; i < device.num_classes; ++i) {
+      switch (device.classes[i]->type) {
+        case XIValuatorClass:
+          valuator_class_infos.push_back(ValuatorClassInfo(
+              *reinterpret_cast<XIValuatorClassInfo*>(device.classes[i])));
+          break;
+        case XITouchClass:
+          // A device can have at most one XITouchClassInfo. Ref:
+          // http://manpages.ubuntu.com/manpages/saucy/man3/XIQueryDevice.3.html
+          DCHECK(!touch_class_info.mode);
+          touch_class_info = TouchClassInfo(
+              *reinterpret_cast<XITouchClassInfo*>(device.classes[i]));
+          break;
+        default:
+          break;
+      }
+    }
+  }
+
+  // Unique device identifier.
+  int id;
+
+  // Internal device name.
+  std::string name;
+
+  // USB-style device identifiers.
+  uint16_t vendor_id;
+  uint16_t product_id;
+
+  // Device type (ie: XIMasterPointer)
+  int use;
+
+  // Specifies the type of the device.
+  DeviceType type;
+
+  // Path to the actual device (ie: /dev/input/eventXX)
+  base::FilePath path;
 
-// Returns true if |name| is the name of a known internal keyboard device. Note,
+  std::vector<ValuatorClassInfo> valuator_class_infos;
+
+  TouchClassInfo touch_class_info;
+};
+
+// X11 display cache used on worker threads. This is filled on the UI thread and
+// passed in to the worker threads.
+struct DisplayState {
+  Atom mt_position_x;
+  Atom mt_position_y;
+};
+
+// Returns true if |name| is the name of a known invalid keyboard device. Note,
 // this may return false negatives.
-bool IsInternalKeyboard(const std::string& name) {
-  // TODO(rsadam@): Come up with a more generic way of identifying internal
-  // keyboards. See crbug.com/420728.
-  if (name == kATKeyboardName)
-    return true;
-  return name.compare(
-             0u, strlen(kCrosEcKeyboardPrefix), kCrosEcKeyboardPrefix) == 0;
+bool IsKnownInvalidKeyboardDevice(const std::string& name) {
+  std::string trimmed(name);
+  base::TrimWhitespaceASCII(name, base::TRIM_TRAILING, &trimmed);
+  for (const char* device_name : kKnownInvalidKeyboardDeviceNames) {
+    if (trimmed == device_name)
+      return true;
+  }
+  return false;
 }
 
 // Returns true if |name| is the name of a known XTEST device. Note, this may
 // return false negatives.
-bool IsTestKeyboard(const std::string& name) {
+bool IsTestDevice(const std::string& name) {
   return name.find("XTEST") != std::string::npos;
 }
 
-// We consider the touchscreen to be internal if it is an I2c device.
-// With the device id, we can query X to get the device's dev input
-// node eventXXX. Then we search all the dev input nodes registered
-// by I2C devices to see if we can find eventXXX.
-bool IsTouchscreenInternal(XDisplay* dpy, int device_id) {
-#if !defined(CHROMEOS)
-  return false;
-#else
-  if (!base::SysInfo::IsRunningOnChromeOS())
-    return false;
-#endif
+base::FilePath GetDevicePath(XDisplay* dpy, const XIDeviceInfo& device) {
+  // Skip the main pointer and keyboard since XOpenDevice() generates a
+  // BadDevice error when passed these devices.
+  if (device.use == XIMasterPointer || device.use == XIMasterKeyboard)
+    return base::FilePath();
 
   // Input device has a property "Device Node" pointing to its dev input node,
   // e.g.   Device Node (250): "/dev/input/event8"
   Atom device_node = XInternAtom(dpy, "Device Node", False);
   if (device_node == None)
-    return false;
+    return base::FilePath();
 
   Atom actual_type;
   int actual_format;
   unsigned long nitems, bytes_after;
   unsigned char* data;
-  XDevice* dev = XOpenDevice(dpy, device_id);
+  XDevice* dev = XOpenDevice(dpy, device.deviceid);
   if (!dev)
-    return false;
+    return base::FilePath();
 
   if (XGetDeviceProperty(dpy,
                          dev,
@@ -98,124 +230,266 @@ bool IsTouchscreenInternal(XDisplay* dpy, int device_id) {
                          &bytes_after,
                          &data) != Success) {
     XCloseDevice(dpy, dev);
-    return false;
+    return base::FilePath();
   }
-  base::FilePath dev_node_path(reinterpret_cast<char*>(data));
+
+  std::string path;
+  // Make sure the returned value is a string.
+  if (actual_type == XA_STRING && actual_format == 8)
+    path = reinterpret_cast<char*>(data);
+
   XFree(data);
   XCloseDevice(dpy, dev);
 
-  return ui::IsTouchscreenInternal(dev_node_path);
+  return base::FilePath(path);
 }
 
-}  // namespace
+// Helper used to parse keyboard information. When it is done it uses
+// |reply_runner| and |callback| to update the state on the UI thread.
+void HandleKeyboardDevicesInWorker(
+    const std::vector<DeviceInfo>& device_infos,
+    scoped_refptr<base::TaskRunner> reply_runner,
+    const KeyboardDeviceCallback& callback) {
+  std::vector<KeyboardDevice> devices;
 
-X11HotplugEventHandler::X11HotplugEventHandler(
-    DeviceHotplugEventObserver* delegate)
-    : delegate_(delegate) {
-}
+  for (const DeviceInfo& device_info : device_infos) {
+    if (device_info.type != DEVICE_TYPE_KEYBOARD)
+      continue;
+    if (device_info.use != XISlaveKeyboard)
+      continue;  // Assume all keyboards are keyboard slaves
+    if (IsKnownInvalidKeyboardDevice(device_info.name))
+      continue;  // Skip invalid devices.
+    InputDeviceType type = GetInputDeviceTypeFromPath(device_info.path);
+    KeyboardDevice keyboard(device_info.id, type, device_info.name);
+    devices.push_back(keyboard);
+  }
 
-X11HotplugEventHandler::~X11HotplugEventHandler() {
+  reply_runner->PostTask(FROM_HERE, base::Bind(callback, devices));
 }
 
-void X11HotplugEventHandler::OnHotplugEvent() {
-  const XIDeviceList& device_list =
-      DeviceListCacheX11::GetInstance()->GetXI2DeviceList(gfx::GetXDisplay());
-  HandleTouchscreenDevices(device_list);
-  HandleKeyboardDevices(device_list);
-}
+// Helper used to parse mouse information. When it is done it uses
+// |reply_runner| and |callback| to update the state on the UI thread.
+void HandleMouseDevicesInWorker(const std::vector<DeviceInfo>& device_infos,
+                                scoped_refptr<base::TaskRunner> reply_runner,
+                                const InputDeviceCallback& callback) {
+  std::vector<InputDevice> devices;
+  for (const DeviceInfo& device_info : device_infos) {
+    if (device_info.type != DEVICE_TYPE_MOUSE ||
+        device_info.use != XISlavePointer) {
+      continue;
+    }
 
-void X11HotplugEventHandler::HandleKeyboardDevices(
-    const XIDeviceList& x11_devices) {
-  std::vector<KeyboardDevice> devices;
+    InputDeviceType type = GetInputDeviceTypeFromPath(device_info.path);
+    devices.push_back(InputDevice(device_info.id, type, device_info.name));
+  }
 
-  for (int i = 0; i < x11_devices.count; i++) {
-    if (!x11_devices[i].enabled || x11_devices[i].use != XISlaveKeyboard)
-      continue;  // Assume all keyboards are keyboard slaves
-    std::string device_name(x11_devices[i].name);
-    base::TrimWhitespaceASCII(device_name, base::TRIM_TRAILING, &device_name);
-    if (IsTestKeyboard(device_name))
-      continue;  // Skip test devices.
-    InputDeviceType type;
-    if (IsInternalKeyboard(device_name)) {
-      type = InputDeviceType::INPUT_DEVICE_INTERNAL;
-    } else if (IsKnownKeyboard(device_name)) {
-      type = InputDeviceType::INPUT_DEVICE_EXTERNAL;
-    } else {
-      type = InputDeviceType::INPUT_DEVICE_UNKNOWN;
+  reply_runner->PostTask(FROM_HERE, base::Bind(callback, devices));
+}
+
+// Helper used to parse touchpad information. When it is done it uses
+// |reply_runner| and |callback| to update the state on the UI thread.
+void HandleTouchpadDevicesInWorker(const std::vector<DeviceInfo>& device_infos,
+                                   scoped_refptr<base::TaskRunner> reply_runner,
+                                   const InputDeviceCallback& callback) {
+  std::vector<InputDevice> devices;
+  for (const DeviceInfo& device_info : device_infos) {
+    if (device_info.type != DEVICE_TYPE_TOUCHPAD ||
+        device_info.use != XISlavePointer) {
+      continue;
     }
-    devices.push_back(
-        KeyboardDevice(x11_devices[i].deviceid, type, device_name));
+
+    InputDeviceType type = GetInputDeviceTypeFromPath(device_info.path);
+    devices.push_back(InputDevice(device_info.id, type, device_info.name));
   }
-  delegate_->OnKeyboardDevicesUpdated(devices);
+
+  reply_runner->PostTask(FROM_HERE, base::Bind(callback, devices));
 }
 
-void X11HotplugEventHandler::HandleTouchscreenDevices(
-    const XIDeviceList& x11_devices) {
+// Helper used to parse touchscreen information. When it is done it uses
+// |reply_runner| and |callback| to update the state on the UI thread.
+void HandleTouchscreenDevicesInWorker(
+    const std::vector<DeviceInfo>& device_infos,
+    const DisplayState& display_state,
+    scoped_refptr<base::TaskRunner> reply_runner,
+    const TouchscreenDeviceCallback& callback) {
   std::vector<TouchscreenDevice> devices;
-  Display* display = gfx::GetXDisplay();
-  Atom valuator_x = XInternAtom(display, "Abs MT Position X", False);
-  Atom valuator_y = XInternAtom(display, "Abs MT Position Y", False);
-  if (valuator_x == None || valuator_y == None)
+  if (display_state.mt_position_x == None ||
+      display_state.mt_position_y == None)
     return;
 
-  std::set<int> no_match_touchscreen;
-  for (int i = 0; i < x11_devices.count; i++) {
-    if (!x11_devices[i].enabled || x11_devices[i].use != XIFloatingSlave)
-      continue;  // Assume all touchscreens are floating slaves
+  for (const DeviceInfo& device_info : device_infos) {
+    if (device_info.type != DEVICE_TYPE_TOUCHSCREEN ||
+        (device_info.use != XIFloatingSlave &&
+         device_info.use != XISlavePointer)) {
+      continue;
+    }
+
+    // Touchscreens should be direct touch devices.
+    if (device_info.touch_class_info.mode != XIDirectTouch)
+      continue;
 
     double max_x = -1.0;
     double max_y = -1.0;
-    bool is_direct_touch = false;
-
-    for (int j = 0; j < x11_devices[i].num_classes; j++) {
-      XIAnyClassInfo* class_info = x11_devices[i].classes[j];
-
-      if (class_info->type == XIValuatorClass) {
-        XIValuatorClassInfo* valuator_info =
-            reinterpret_cast<XIValuatorClassInfo*>(class_info);
-
-        if (valuator_x == valuator_info->label) {
-          // Ignore X axis valuator with unexpected properties
-          if (valuator_info->number == 0 && valuator_info->mode == Absolute &&
-              valuator_info->min == 0.0) {
-            max_x = valuator_info->max;
-          }
-        } else if (valuator_y == valuator_info->label) {
-          // Ignore Y axis valuator with unexpected properties
-          if (valuator_info->number == 1 && valuator_info->mode == Absolute &&
-              valuator_info->min == 0.0) {
-            max_y = valuator_info->max;
-          }
+
+    for (const ValuatorClassInfo& valuator : device_info.valuator_class_infos) {
+      if (display_state.mt_position_x == valuator.label) {
+        // Ignore X axis valuator with unexpected properties
+        if (valuator.number == 0 && valuator.mode == Absolute &&
+            valuator.min == 0.0) {
+          max_x = valuator.max;
+        }
+      } else if (display_state.mt_position_y == valuator.label) {
+        // Ignore Y axis valuator with unexpected properties
+        if (valuator.number == 1 && valuator.mode == Absolute &&
+            valuator.min == 0.0) {
+          max_y = valuator.max;
         }
       }
-#if defined(USE_XI2_MT)
-      if (class_info->type == XITouchClass) {
-        XITouchClassInfo* touch_info =
-            reinterpret_cast<XITouchClassInfo*>(class_info);
-        is_direct_touch = touch_info->mode == XIDirectTouch;
-      }
-#endif
     }
 
-    // Touchscreens should have absolute X and Y axes, and be direct touch
-    // devices.
-    if (max_x > 0.0 && max_y > 0.0 && is_direct_touch) {
-      InputDeviceType type =
-          IsTouchscreenInternal(display, x11_devices[i].deviceid)
-              ? InputDeviceType::INPUT_DEVICE_INTERNAL
-              : InputDeviceType::INPUT_DEVICE_EXTERNAL;
-      std::string name(x11_devices[i].name);
+    // Touchscreens should have absolute X and Y axes.
+    if (max_x > 0.0 && max_y > 0.0) {
+      InputDeviceType type = GetInputDeviceTypeFromPath(device_info.path);
       // |max_x| and |max_y| are inclusive values, so we need to add 1 to get
       // the size.
-      devices.push_back(TouchscreenDevice(
-          x11_devices[i].deviceid,
-          type,
-          name,
-          gfx::Size(max_x + 1, max_y + 1)));
+      devices.push_back(
+          TouchscreenDevice(device_info.id, type, device_info.name,
+                            gfx::Size(max_x + 1, max_y + 1),
+                            device_info.touch_class_info.num_touches));
+    }
+  }
+
+  reply_runner->PostTask(FROM_HERE, base::Bind(callback, devices));
+}
+
+// Called on a worker thread to parse the device information.
+void HandleHotplugEventInWorker(
+    const std::vector<DeviceInfo>& devices,
+    const DisplayState& display_state,
+    scoped_refptr<base::TaskRunner> reply_runner,
+    const UiCallbacks& callbacks) {
+  HandleTouchscreenDevicesInWorker(
+      devices, display_state, reply_runner, callbacks.touchscreen_callback);
+  HandleKeyboardDevicesInWorker(
+      devices, reply_runner, callbacks.keyboard_callback);
+  HandleMouseDevicesInWorker(devices, reply_runner, callbacks.mouse_callback);
+  HandleTouchpadDevicesInWorker(devices, reply_runner,
+                                callbacks.touchpad_callback);
+}
+
+DeviceHotplugEventObserver* GetHotplugEventObserver() {
+  return DeviceDataManager::GetInstance();
+}
+
+void OnKeyboardDevices(const std::vector<KeyboardDevice>& devices) {
+  GetHotplugEventObserver()->OnKeyboardDevicesUpdated(devices);
+}
+
+void OnTouchscreenDevices(const std::vector<TouchscreenDevice>& devices) {
+  GetHotplugEventObserver()->OnTouchscreenDevicesUpdated(devices);
+}
+
+void OnMouseDevices(const std::vector<InputDevice>& devices) {
+  GetHotplugEventObserver()->OnMouseDevicesUpdated(devices);
+}
+
+void OnTouchpadDevices(const std::vector<InputDevice>& devices) {
+  GetHotplugEventObserver()->OnTouchpadDevicesUpdated(devices);
+}
+
+}  // namespace
+
+X11HotplugEventHandler::X11HotplugEventHandler()
+    : atom_cache_(gfx::GetXDisplay(), kCachedAtomList) {
+}
+
+X11HotplugEventHandler::~X11HotplugEventHandler() {
+}
+
+void X11HotplugEventHandler::OnHotplugEvent() {
+  Display* display = gfx::GetXDisplay();
+  const XDeviceList& device_list_xi =
+      DeviceListCacheX11::GetInstance()->GetXDeviceList(display);
+  const XIDeviceList& device_list_xi2 =
+      DeviceListCacheX11::GetInstance()->GetXI2DeviceList(display);
+
+  const int kMaxDeviceNum = 128;
+  DeviceType device_types[kMaxDeviceNum];
+  for (int i = 0; i < kMaxDeviceNum; ++i)
+    device_types[i] = DEVICE_TYPE_OTHER;
+
+  for (int i = 0; i < device_list_xi.count; ++i) {
+    int id = device_list_xi[i].id;
+    if (id < 0 || id >= kMaxDeviceNum)
+      continue;
+
+    Atom type = device_list_xi[i].type;
+    if (type == atom_cache_.GetAtom(XI_KEYBOARD))
+      device_types[id] = DEVICE_TYPE_KEYBOARD;
+    else if (type == atom_cache_.GetAtom(XI_MOUSE))
+      device_types[id] = DEVICE_TYPE_MOUSE;
+    else if (type == atom_cache_.GetAtom(XI_TOUCHPAD))
+      device_types[id] = DEVICE_TYPE_TOUCHPAD;
+    else if (type == atom_cache_.GetAtom(XI_TOUCHSCREEN))
+      device_types[id] = DEVICE_TYPE_TOUCHSCREEN;
+  }
+
+  std::vector<DeviceInfo> device_infos;
+  for (int i = 0; i < device_list_xi2.count; ++i) {
+    const XIDeviceInfo& device = device_list_xi2[i];
+    if (!device.enabled || IsTestDevice(device.name))
+      continue;
+
+    DeviceType device_type =
+        (device.deviceid >= 0 && device.deviceid < kMaxDeviceNum)
+            ? device_types[device.deviceid]
+            : DEVICE_TYPE_OTHER;
+
+    // Obtain the USB-style vendor and product identifiers.
+    // (On Linux, XI2 makes this available for all evdev devices.
+    uint32_t* product_info;
+    Atom type;
+    int format_return;
+    unsigned long num_items_return;
+    unsigned long bytes_after_return;
+    uint16_t vendor = 0;
+    uint16_t product = 0;
+    if (XIGetProperty(gfx::GetXDisplay(), device.deviceid,
+                      atom_cache_.GetAtom(XI_PROP_PRODUCT_ID), 0, 2, 0,
+                      XA_INTEGER, &type, &format_return, &num_items_return,
+                      &bytes_after_return,
+                      reinterpret_cast<unsigned char**>(&product_info)) == 0 &&
+        product_info) {
+      if (num_items_return == 2) {
+        vendor = product_info[0];
+        product = product_info[1];
+      }
+      XFree(product_info);
     }
+
+    device_infos.push_back(DeviceInfo(
+        device, device_type, GetDevicePath(display, device), vendor, product));
   }
 
-  delegate_->OnTouchscreenDevicesUpdated(devices);
+  // X11 is not thread safe, so first get all the required state.
+  DisplayState display_state;
+  display_state.mt_position_x = atom_cache_.GetAtom("Abs MT Position X");
+  display_state.mt_position_y = atom_cache_.GetAtom("Abs MT Position Y");
+
+  UiCallbacks callbacks;
+  callbacks.keyboard_callback = base::Bind(&OnKeyboardDevices);
+  callbacks.touchscreen_callback = base::Bind(&OnTouchscreenDevices);
+  callbacks.mouse_callback = base::Bind(&OnMouseDevices);
+  callbacks.touchpad_callback = base::Bind(&OnTouchpadDevices);
+
+  // Parsing the device information may block, so delegate the operation to a
+  // worker thread. Once the device information is extracted the parsed devices
+  // will be returned via the callbacks.
+  base::WorkerPool::PostTask(
+      FROM_HERE,
+      base::Bind(&HandleHotplugEventInWorker, device_infos, display_state,
+                 base::ThreadTaskRunnerHandle::Get(), callbacks),
+      true /* task_is_slow */);
 }
 
 }  // namespace ui