1 files changed, 290 insertions, 94 deletions

diff --git a/Source/WebCore/page/DOMTimer.cpp b/Source/WebCore/page/DOMTimer.cpp
index 0c99e0d39..80e1b8d68 100644
--- a/Source/WebCore/page/DOMTimer.cpp
+++ b/Source/WebCore/page/DOMTimer.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008 Apple Inc. All Rights Reserved.
+ * Copyright (C) 2008, 2014 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -10,10 +10,10 @@
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
- * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
@@ -27,73 +27,191 @@
 #include "config.h"
 #include "DOMTimer.h"
 
+#include "HTMLPlugInElement.h"
 #include "InspectorInstrumentation.h"
+#include "Logging.h"
+#include "Page.h"
+#include "PluginViewBase.h"
 #include "ScheduledAction.h"
 #include "ScriptExecutionContext.h"
-#include "UserGestureIndicator.h"
+#include "Settings.h"
 #include <wtf/CurrentTime.h>
-#include <wtf/HashSet.h>
+#include <wtf/HashMap.h>
+#include <wtf/MathExtras.h>
+#include <wtf/NeverDestroyed.h>
+#include <wtf/RandomNumber.h>
 #include <wtf/StdLibExtras.h>
 
 #if PLATFORM(IOS)
 #include "Chrome.h"
 #include "ChromeClient.h"
 #include "Frame.h"
-#include "Page.h"
 #include "WKContentObservation.h"
+#include "WKContentObservationInternal.h"
 #endif
 
 namespace WebCore {
 
-static const int maxIntervalForUserGestureForwarding = 1000; // One second matches Gecko.
+static const auto maxIntervalForUserGestureForwarding = 1000ms; // One second matches Gecko.
+static const auto minIntervalForNonUserObservableChangeTimers = 1000ms; // Empirically determined to maximize battery life.
 static const int maxTimerNestingLevel = 5;
-static const double oneMillisecond = 0.001;
 
-static int timerNestingLevel = 0;
-    
-static inline bool shouldForwardUserGesture(int interval, int nestingLevel)
+class DOMTimerFireState {
+public:
+    explicit DOMTimerFireState(ScriptExecutionContext& context)
+        : m_context(context)
+        , m_contextIsDocument(is<Document>(m_context))
+    {
+        // For worker threads, don't update the current DOMTimerFireState.
+        // Setting this from workers would not be thread-safe, and its not relevant to current uses.
+        if (m_contextIsDocument) {
+            m_initialDOMTreeVersion = downcast<Document>(context).domTreeVersion();
+            m_previous = current;
+            current = this;
+        }
+    }
+
+    ~DOMTimerFireState()
+    {
+        if (m_contextIsDocument)
+            current = m_previous;
+    }
+
+    Document* contextDocument() const { return m_contextIsDocument ? &downcast<Document>(m_context) : nullptr; }
+
+    void setScriptMadeUserObservableChanges() { m_scriptMadeUserObservableChanges = true; }
+    void setScriptMadeNonUserObservableChanges() { m_scriptMadeNonUserObservableChanges = true; }
+
+    bool scriptMadeNonUserObservableChanges() const { return m_scriptMadeNonUserObservableChanges; }
+    bool scriptMadeUserObservableChanges() const
+    {
+        if (m_scriptMadeUserObservableChanges)
+            return true;
+
+        Document* document = contextDocument();
+        // To be conservative, we also consider any DOM Tree change to be user observable.
+        return document && document->domTreeVersion() != m_initialDOMTreeVersion;
+    }
+
+    static DOMTimerFireState* current;
+
+private:
+    ScriptExecutionContext& m_context;
+    uint64_t m_initialDOMTreeVersion;
+    DOMTimerFireState* m_previous;
+    bool m_contextIsDocument;
+    bool m_scriptMadeNonUserObservableChanges { false };
+    bool m_scriptMadeUserObservableChanges { false };
+};
+
+DOMTimerFireState* DOMTimerFireState::current = nullptr;
+
+struct NestedTimersMap {
+    typedef HashMap<int, DOMTimer*>::const_iterator const_iterator;
+
+    static NestedTimersMap* instanceForContext(ScriptExecutionContext& context)
+    {
+        // For worker threads, we don't use NestedTimersMap as doing so would not
+        // be thread safe.
+        if (is<Document>(context))
+            return &instance();
+        return nullptr;
+    }
+
+    void startTracking()
+    {
+        // Make sure we start with an empty HashMap. In theory, it is possible the HashMap is not
+        // empty if a timer fires during the execution of another timer (may happen with the
+        // in-process Web Inspector).
+        nestedTimers.clear();
+        isTrackingNestedTimers = true;
+    }
+
+    void stopTracking()
+    {
+        isTrackingNestedTimers = false;
+        nestedTimers.clear();
+    }
+
+    void add(int timeoutId, DOMTimer* timer)
+    {
+        if (isTrackingNestedTimers)
+            nestedTimers.add(timeoutId, timer);
+    }
+
+    void remove(int timeoutId)
+    {
+        if (isTrackingNestedTimers)
+            nestedTimers.remove(timeoutId);
+    }
+
+    const_iterator begin() const { return nestedTimers.begin(); }
+    const_iterator end() const { return nestedTimers.end(); }
+
+private:
+    static NestedTimersMap& instance()
+    {
+        static NeverDestroyed<NestedTimersMap> map;
+        return map;
+    }
+
+    static bool isTrackingNestedTimers;
+    HashMap<int /* timeoutId */, DOMTimer*> nestedTimers;
+};
+
+bool NestedTimersMap::isTrackingNestedTimers = false;
+
+static inline bool shouldForwardUserGesture(std::chrono::milliseconds interval, int nestingLevel)
 {
     return UserGestureIndicator::processingUserGesture()
         && interval <= maxIntervalForUserGestureForwarding
-        && nestingLevel == 1; // Gestures should not be forwarded to nested timers.
+        && !nestingLevel; // Gestures should not be forwarded to nested timers.
+}
+
+static inline RefPtr<UserGestureToken> userGestureTokenToForward(std::chrono::milliseconds interval, int nestingLevel)
+{
+    if (!shouldForwardUserGesture(interval, nestingLevel))
+        return nullptr;
+
+    return UserGestureIndicator::currentUserGesture();
 }
 
-DOMTimer::DOMTimer(ScriptExecutionContext* context, PassOwnPtr<ScheduledAction> action, int interval, bool singleShot)
+DOMTimer::DOMTimer(ScriptExecutionContext& context, std::unique_ptr<ScheduledAction> action, std::chrono::milliseconds interval, bool singleShot)
     : SuspendableTimer(context)
-    , m_nestingLevel(timerNestingLevel + 1)
-    , m_action(action)
+    , m_nestingLevel(context.timerNestingLevel())
+    , m_action(WTFMove(action))
     , m_originalInterval(interval)
-    , m_shouldForwardUserGesture(shouldForwardUserGesture(interval, m_nestingLevel))
+    , m_throttleState(Undetermined)
+    , m_currentTimerInterval(intervalClampedToMinimum())
+    , m_userGestureTokenToForward(userGestureTokenToForward(interval, m_nestingLevel))
 {
+    RefPtr<DOMTimer> reference = adoptRef(this);
+
     // Keep asking for the next id until we're given one that we don't already have.
     do {
-        m_timeoutId = context->circularSequentialID();
-    } while (!context->addTimeout(m_timeoutId, this));
+        m_timeoutId = context.circularSequentialID();
+    } while (!context.addTimeout(m_timeoutId, *this));
 
-    double intervalMilliseconds = intervalClampedToMinimum(interval, context->minimumTimerInterval());
     if (singleShot)
-        startOneShot(intervalMilliseconds);
+        startOneShot(m_currentTimerInterval);
     else
-        startRepeating(intervalMilliseconds);
+        startRepeating(m_currentTimerInterval);
 }
 
 DOMTimer::~DOMTimer()
 {
-    if (scriptExecutionContext())
-        scriptExecutionContext()->removeTimeout(m_timeoutId);
 }
 
-int DOMTimer::install(ScriptExecutionContext* context, PassOwnPtr<ScheduledAction> action, int timeout, bool singleShot)
+int DOMTimer::install(ScriptExecutionContext& context, std::unique_ptr<ScheduledAction> action, std::chrono::milliseconds timeout, bool singleShot)
 {
-    // DOMTimer constructor links the new timer into a list of ActiveDOMObjects held by the 'context'.
-    // The timer is deleted when context is deleted (DOMTimer::contextDestroyed) or explicitly via DOMTimer::removeById(),
-    // or if it is a one-time timer and it has fired (DOMTimer::fired).
-    DOMTimer* timer = new DOMTimer(context, action, timeout, singleShot);
+    // DOMTimer constructor passes ownership of the initial ref on the object to the constructor.
+    // This reference will be released automatically when a one-shot timer fires, when the context
+    // is destroyed, or if explicitly cancelled by removeById. 
+    DOMTimer* timer = new DOMTimer(context, WTFMove(action), timeout, singleShot);
 #if PLATFORM(IOS)
-    if (context->isDocument()) {
-        Document& document = toDocument(*context);
-        bool didDeferTimeout = document.frame() && document.frame()->timersPaused();
-        if (!didDeferTimeout && timeout <= 100 && singleShot) {
+    if (is<Document>(context)) {
+        bool didDeferTimeout = context.activeDOMObjectsAreSuspended();
+        if (!didDeferTimeout && timeout.count() <= 100 && singleShot) {
             WKSetObservedContentChange(WKContentIndeterminateChange);
             WebThreadAddObservedContentModifier(timer); // Will only take affect if not already visibility change.
         }
@@ -103,10 +221,14 @@ int DOMTimer::install(ScriptExecutionContext* context, PassOwnPtr<ScheduledActio
     timer->suspendIfNeeded();
     InspectorInstrumentation::didInstallTimer(context, timer->m_timeoutId, timeout, singleShot);
 
+    // Keep track of nested timer installs.
+    if (NestedTimersMap* nestedTimers = NestedTimersMap::instanceForContext(context))
+        nestedTimers->add(timer->m_timeoutId, timer);
+
     return timer->m_timeoutId;
 }
 
-void DOMTimer::removeById(ScriptExecutionContext* context, int timeoutId)
+void DOMTimer::removeById(ScriptExecutionContext& context, int timeoutId)
 {
     // timeout IDs have to be positive, and 0 and -1 are unsafe to
     // even look up since they are the empty and deleted value
@@ -114,58 +236,105 @@ void DOMTimer::removeById(ScriptExecutionContext* context, int timeoutId)
     if (timeoutId <= 0)
         return;
 
+    if (NestedTimersMap* nestedTimers = NestedTimersMap::instanceForContext(context))
+        nestedTimers->remove(timeoutId);
+
     InspectorInstrumentation::didRemoveTimer(context, timeoutId);
+    context.removeTimeout(timeoutId);
+}
 
-    delete context->findTimeout(timeoutId);
+inline bool DOMTimer::isDOMTimersThrottlingEnabled(Document& document) const
+{
+    auto* page = document.page();
+    if (!page)
+        return true;
+    return page->settings().domTimersThrottlingEnabled();
 }
 
-void DOMTimer::fired()
+void DOMTimer::updateThrottlingStateIfNecessary(const DOMTimerFireState& fireState)
 {
-    ScriptExecutionContext* context = scriptExecutionContext();
-    ASSERT(context);
-#if PLATFORM(IOS)
-    Document* document = nullptr;
-    if (!context->isDocument()) {
-        document = toDocument(context);
-        ASSERT(!document->frame()->timersPaused());
+    Document* contextDocument = fireState.contextDocument();
+    // We don't throttle timers in worker threads.
+    if (!contextDocument)
+        return;
+
+    if (UNLIKELY(!isDOMTimersThrottlingEnabled(*contextDocument))) {
+        if (m_throttleState == ShouldThrottle) {
+            // Unthrottle the timer in case it was throttled before the setting was updated.
+            LOG(DOMTimers, "%p - Unthrottling DOM timer because throttling was disabled via settings.", this);
+            m_throttleState = ShouldNotThrottle;
+            updateTimerIntervalIfNecessary();
+        }
+        return;
     }
-#endif
-    timerNestingLevel = m_nestingLevel;
+
+    if (fireState.scriptMadeUserObservableChanges()) {
+        if (m_throttleState != ShouldNotThrottle) {
+            m_throttleState = ShouldNotThrottle;
+            updateTimerIntervalIfNecessary();
+        }
+    } else if (fireState.scriptMadeNonUserObservableChanges()) {
+        if (m_throttleState != ShouldThrottle) {
+            m_throttleState = ShouldThrottle;
+            updateTimerIntervalIfNecessary();
+        }
+    }
+}
+
+void DOMTimer::scriptDidInteractWithPlugin(HTMLPlugInElement& pluginElement)
+{
+    if (!DOMTimerFireState::current)
+        return;
+
+    if (pluginElement.isUserObservable())
+        DOMTimerFireState::current->setScriptMadeUserObservableChanges();
+    else
+        DOMTimerFireState::current->setScriptMadeNonUserObservableChanges();
+}
+
+void DOMTimer::fired()
+{
+    // Retain this - if the timer is cancelled while this function is on the stack (implicitly and always
+    // for one-shot timers, or if removeById is called on itself from within an interval timer fire) then
+    // wait unit the end of this function to delete DOMTimer.
+    RefPtr<DOMTimer> reference = this;
+
+    ASSERT(scriptExecutionContext());
+    ScriptExecutionContext& context = *scriptExecutionContext();
+
+    DOMTimerFireState fireState(context);
+
+    context.setTimerNestingLevel(std::min(m_nestingLevel + 1, maxTimerNestingLevel));
+
     ASSERT(!isSuspended());
-    ASSERT(!context->activeDOMObjectsAreSuspended());
-    UserGestureIndicator gestureIndicator(m_shouldForwardUserGesture ? DefinitelyProcessingUserGesture : PossiblyProcessingUserGesture);
+    ASSERT(!context.activeDOMObjectsAreSuspended());
+    UserGestureIndicator gestureIndicator(m_userGestureTokenToForward);
     // Only the first execution of a multi-shot timer should get an affirmative user gesture indicator.
-    m_shouldForwardUserGesture = false;
+    m_userGestureTokenToForward = nullptr;
 
     InspectorInstrumentationCookie cookie = InspectorInstrumentation::willFireTimer(context, m_timeoutId);
 
     // Simple case for non-one-shot timers.
     if (isActive()) {
-        double minimumInterval = context->minimumTimerInterval();
-        if (repeatInterval() && repeatInterval() < minimumInterval) {
+        if (m_nestingLevel < maxTimerNestingLevel) {
             m_nestingLevel++;
-            if (m_nestingLevel >= maxTimerNestingLevel)
-                augmentRepeatInterval(minimumInterval - repeatInterval());
+            updateTimerIntervalIfNecessary();
         }
 
-        // No access to member variables after this point, it can delete the timer.
         m_action->execute(context);
 
         InspectorInstrumentation::didFireTimer(cookie);
+        updateThrottlingStateIfNecessary(fireState);
 
         return;
     }
 
-    // Delete timer before executing the action for one-shot timers.
-    OwnPtr<ScheduledAction> action = m_action.release();
-
-    // No access to member variables after this point.
-    delete this;
+    context.removeTimeout(m_timeoutId);
 
 #if PLATFORM(IOS)
     bool shouldReportLackOfChanges;
     bool shouldBeginObservingChanges;
-    if (document) {
+    if (is<Document>(context)) {
         shouldReportLackOfChanges = WebThreadCountOfObservedContentModifiers() == 1;
         shouldBeginObservingChanges = WebThreadContainsObservedContentModifier(this);
     } else {
@@ -179,27 +348,38 @@ void DOMTimer::fired()
     }
 #endif
 
-    action->execute(context);
+    // Keep track nested timer installs.
+    NestedTimersMap* nestedTimers = NestedTimersMap::instanceForContext(context);
+    if (nestedTimers)
+        nestedTimers->startTracking();
+
+    m_action->execute(context);
 
 #if PLATFORM(IOS)
     if (shouldBeginObservingChanges) {
         WKStopObservingContentChanges();
 
-        if (WKObservedContentChange() == WKContentVisibilityChange || shouldReportLackOfChanges)
-            if (document && document->page())
-                document->page()->chrome().client().observedContentChange(document->frame());
+        if (WKObservedContentChange() == WKContentVisibilityChange || shouldReportLackOfChanges) {
+            Document& document = downcast<Document>(context);
+            if (Page* page = document.page())
+                page->chrome().client().observedContentChange(*document.frame());
+        }
     }
 #endif
 
     InspectorInstrumentation::didFireTimer(cookie);
 
-    timerNestingLevel = 0;
-}
+    // Check if we should throttle nested single-shot timers.
+    if (nestedTimers) {
+        for (auto& keyValue : *nestedTimers) {
+            auto* timer = keyValue.value;
+            if (timer->isActive() && !timer->repeatInterval())
+                timer->updateThrottlingStateIfNecessary(fireState);
+        }
+        nestedTimers->stopTracking();
+    }
 
-void DOMTimer::contextDestroyed()
-{
-    SuspendableTimer::contextDestroyed();
-    delete this;
+    context.setTimerNestingLevel(0);
 }
 
 void DOMTimer::didStop()
@@ -207,48 +387,64 @@ void DOMTimer::didStop()
     // Need to release JS objects potentially protected by ScheduledAction
     // because they can form circular references back to the ScriptExecutionContext
     // which will cause a memory leak.
-    m_action.clear();
+    m_action = nullptr;
 }
 
-void DOMTimer::adjustMinimumTimerInterval(double oldMinimumTimerInterval)
+void DOMTimer::updateTimerIntervalIfNecessary()
 {
-    if (m_nestingLevel < maxTimerNestingLevel)
-        return;
+    ASSERT(m_nestingLevel <= maxTimerNestingLevel);
 
-    double newMinimumInterval = scriptExecutionContext()->minimumTimerInterval();
-    double newClampedInterval = intervalClampedToMinimum(m_originalInterval, newMinimumInterval);
+    auto previousInterval = m_currentTimerInterval;
+    m_currentTimerInterval = intervalClampedToMinimum();
+    if (previousInterval == m_currentTimerInterval)
+        return;
 
     if (repeatInterval()) {
-        augmentRepeatInterval(newClampedInterval - repeatInterval());
-        return;
+        ASSERT(repeatIntervalMS() == previousInterval);
+        LOG(DOMTimers, "%p - Updating DOMTimer's repeat interval from %" PRId64 " ms to %" PRId64 " ms due to throttling.", this, previousInterval.count(), m_currentTimerInterval.count());
+        augmentRepeatInterval(m_currentTimerInterval - previousInterval);
+    } else {
+        LOG(DOMTimers, "%p - Updating DOMTimer's fire interval from %" PRId64 " ms to %" PRId64 " ms due to throttling.", this, previousInterval.count(), m_currentTimerInterval.count());
+        augmentFireInterval(m_currentTimerInterval - previousInterval);
     }
-
-    double previousClampedInterval = intervalClampedToMinimum(m_originalInterval, oldMinimumTimerInterval);
-    augmentFireInterval(newClampedInterval - previousClampedInterval);
 }
 
-double DOMTimer::intervalClampedToMinimum(int timeout, double minimumTimerInterval) const
+std::chrono::milliseconds DOMTimer::intervalClampedToMinimum() const
 {
-    double intervalMilliseconds = std::max(oneMillisecond, timeout * oneMillisecond);
+    ASSERT(scriptExecutionContext());
+    ASSERT(m_nestingLevel <= maxTimerNestingLevel);
+
+    auto interval = std::max(1ms, m_originalInterval);
+
+    // Only apply throttling to repeating timers.
+    if (m_nestingLevel < maxTimerNestingLevel)
+        return interval;
 
-    if (intervalMilliseconds < minimumTimerInterval && m_nestingLevel >= maxTimerNestingLevel)
-        intervalMilliseconds = minimumTimerInterval;
-    return intervalMilliseconds;
+    // Apply two throttles - the global (per Page) minimum, and also a per-timer throttle.
+    interval = std::max(interval, scriptExecutionContext()->minimumTimerInterval());
+    if (m_throttleState == ShouldThrottle)
+        interval = std::max(interval, minIntervalForNonUserObservableChangeTimers);
+    return interval;
 }
 
-double DOMTimer::alignedFireTime(double fireTime) const
+std::optional<std::chrono::milliseconds> DOMTimer::alignedFireTime(std::chrono::milliseconds fireTime) const
 {
-    double alignmentInterval = scriptExecutionContext()->timerAlignmentInterval();
-    if (alignmentInterval) {
-        double currentTime = monotonicallyIncreasingTime();
-        if (fireTime <= currentTime)
-            return fireTime;
+    auto alignmentInterval = scriptExecutionContext()->timerAlignmentInterval(m_nestingLevel >= maxTimerNestingLevel);
+    if (alignmentInterval == 0ms)
+        return std::nullopt;
+    
+    static const double randomizedProportion = randomNumber();
 
-        double alignedTime = ceil(fireTime / alignmentInterval) * alignmentInterval;
-        return alignedTime;
-    }
+    // Force alignment to randomizedAlignment fraction of the way between alignemntIntervals, e.g.
+    // if alignmentInterval is 10 and randomizedAlignment is 0.3 this will align to 3, 13, 23, ...
+    auto randomizedOffset = std::chrono::duration_cast<std::chrono::milliseconds>(alignmentInterval * randomizedProportion);
+    auto adjustedFireTime = fireTime - randomizedOffset;
+    return adjustedFireTime - (adjustedFireTime % alignmentInterval) + alignmentInterval + randomizedOffset;
+}
 
-    return fireTime;
+const char* DOMTimer::activeDOMObjectName() const
+{
+    return "DOMTimer";
 }
 
 } // namespace WebCore