Free temporary GPU and memory resources held by inactive or hidden 2D canvases

Source/platform/graphics/Canvas2DLayerBridge.h

Index: Source/platform/graphics/Canvas2DLayerBridge.h
diff --git a/Source/platform/graphics/Canvas2DLayerBridge.h b/Source/platform/graphics/Canvas2DLayerBridge.h
index d259c5fcd9d678c4bc10e7f701853ece552f9247..c2983a2c75d1caf3c4195ec563a9184d1e13400a 100644
--- a/Source/platform/graphics/Canvas2DLayerBridge.h
+++ b/Source/platform/graphics/Canvas2DLayerBridge.h
@@ -48,10 +48,17 @@ class Canvas2DLayerBridgeTest;
 
 namespace WebCore {
 
+class Canvas2DLayerBridgeClient {
+public:
+    virtual bool hidden() const = 0;
+    virtual ~Canvas2DLayerBridgeClient() { }
+};
+
 class PLATFORM_EXPORT Canvas2DLayerBridge : public blink::WebExternalTextureLayerClient, public SkDeferredCanvas::NotificationClient, public DoublyLinkedListNode<Canvas2DLayerBridge>, public RefCounted<Canvas2DLayerBridge> {
     WTF_MAKE_NONCOPYABLE(Canvas2DLayerBridge);
 public:
-    static PassRefPtr<Canvas2DLayerBridge> create(const IntSize&, OpacityMode, int msaaSampleCount);
+    static PassRefPtr<Canvas2DLayerBridge> create(Canvas2DLayerBridgeClient*, const IntSize&, OpacityMode, int msaaSampleCount);
+
     virtual ~Canvas2DLayerBridge();
 
     // blink::WebExternalTextureLayerClient implementation.
@@ -77,15 +84,21 @@ public:
     virtual size_t freeMemoryIfPossible(size_t); // virtual for mocking
     virtual void flush(); // virtual for mocking
     virtual size_t storageAllocatedForRecording(); // virtual for faking
-    size_t bytesAllocated() const {return m_bytesAllocated;}
+    size_t bytesAllocated() const { return m_bytesAllocated; }
     void limitPendingFrames();
+    void freeReleasedMailbox();
+    bool hasReleasedMailbox() const { return m_releasedMailboxInfo; };
+    void freeTransientResources();
+    bool hasTransientResources() const;
+    bool hidden() const;
 
     void beginDestruction();
 
 protected:
-    Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D>, PassOwnPtr<SkDeferredCanvas>, int, OpacityMode);
+    Canvas2DLayerBridge(Canvas2DLayerBridgeClient*, PassRefPtr<GraphicsContext3D>, PassOwnPtr<SkDeferredCanvas>, int, OpacityMode);
     void setRateLimitingEnabled(bool);
 
+    Canvas2DLayerBridgeClient* m_client;
     OwnPtr<SkDeferredCanvas> m_canvas;
     OwnPtr<blink::WebExternalTextureLayer> m_layer;
     RefPtr<GraphicsContext3D> m_context;
@@ -94,6 +107,7 @@ protected:
     bool m_didRecordDrawCommand;
     bool m_surfaceIsValid;
     int m_framesPending;
+    int m_framesSinceMailboxRelease;
     bool m_destructionInProgress;
     bool m_rateLimitingEnabled;
 
@@ -110,7 +124,7 @@ protected:
 
     struct MailboxInfo {
         blink::WebExternalTextureMailbox m_mailbox;
-        SkAutoTUnref<SkImage> m_image;
+        RefPtr<SkImage> m_image;
         MailboxStatus m_status;
         RefPtr<Canvas2DLayerBridge> m_parentLayerBridge;
 
@@ -121,6 +135,7 @@ protected:
 
     uint32_t m_lastImageId;
     Vector<MailboxInfo> m_mailboxes;
+    MailboxInfo* m_releasedMailboxInfo;
 };
 }
 #endif