1 files changed, 65 insertions, 0 deletions
diff --git a/chromium/components/viz/service/display_embedder/output_device_backing.h b/chromium/components/viz/service/display_embedder/output_device_backing.h
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index 00000000000..b3a9b1cb81c
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+++ b/chromium/components/viz/service/display_embedder/output_device_backing.h
@@ -0,0 +1,65 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_VIZ_SERVICE_DISPLAY_EMBEDDER_OUTPUT_DEVICE_BACKING_H_
+#define COMPONENTS_VIZ_SERVICE_DISPLAY_EMBEDDER_OUTPUT_DEVICE_BACKING_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+#include "components/viz/service/viz_service_export.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace base {
+class SharedMemory;
+}
+
+namespace viz {
+
+// Allocates and owns a SharedMemory backing for multiple SoftwareOutputDevices.
+// The backing will be big enough to hold the largest size returned by a
+// client's GetViewportPixelSize().
+class VIZ_SERVICE_EXPORT OutputDeviceBacking {
+ public:
+  class Client {
+   public:
+    virtual const gfx::Size& GetViewportPixelSize() const = 0;
+    virtual void ReleaseCanvas() = 0;
+
+   protected:
+    virtual ~Client() = default;
+  };
+
+  OutputDeviceBacking();
+  ~OutputDeviceBacking();
+
+  void RegisterClient(Client* client);
+  void UnregisterClient(Client* client);
+
+  // Called when a client has resized. Clients should call Resize() after being
+  // registered when they have a valid size. Will potential invalidate
+  // SharedMemory and call ReleaseCanvas() on clients.
+  void ClientResized();
+
+  // Requests a SharedMemory segment large enough to fit |viewport_size|. Will
+  // return null if |viewport_size| is too large to safely allocate SharedMemory
+  // for.
+  base::SharedMemory* GetSharedMemory(const gfx::Size& viewport_size);
+
+  // Returns the maximum size in bytes needed for the largest viewport from
+  // registered clients.
+  size_t GetMaxViewportBytes();
+
+ private:
+  std::vector<Client*> clients_;
+  std::unique_ptr<base::SharedMemory> shm_;
+  size_t created_shm_bytes_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(OutputDeviceBacking);
+};
+
+}  // namespace viz
+
+#endif  // COMPONENTS_VIZ_SERVICE_DISPLAY_EMBEDDER_OUTPUT_DEVICE_BACKING_H_