Change Canvas2DLayerBridge to stay alive until last mailbox is returned.

Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 25 matching lines @@
 #include "wtf/DoublyLinkedList.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace WebKit {
 class WebGraphicsContext3D;
 }
 
 namespace WebCore {
 
-class Canvas2DLayerBridge : public WebKit::WebExternalTextureLayerClient, public SkDeferredCanvas::NotificationClient, public DoublyLinkedListNode<Canvas2DLayerBridge> {
+class Canvas2DLayerBridge;
+
+class Canvas2DLayerBridgePtr {
+public:
+    Canvas2DLayerBridgePtr() { }
+    Canvas2DLayerBridgePtr(PassRefPtr<Canvas2DLayerBridge> ptr) { m_ptr = ptr; }
+    Canvas2DLayerBridgePtr(const Canvas2DLayerBridgePtr&);
+    ~Canvas2DLayerBridgePtr() { clear(); }
+    Canvas2DLayerBridge* operator->() const { return m_ptr.get(); }
+    Canvas2DLayerBridgePtr& operator=(const Canvas2DLayerBridgePtr&);
+    Canvas2DLayerBridge* get() const { return m_ptr.get(); }
+    operator bool () const { return m_ptr; }
+    void clear();

[Stephen White, 2013/08/23 14:45:28]

Nit: looks like this function is only called from the destructor; could just put
its contents there and remove it.

+private:
+    RefPtr<Canvas2DLayerBridge> m_ptr;
+};
+
+class Canvas2DLayerBridge : public WebKit::WebExternalTextureLayerClient, public SkDeferredCanvas::NotificationClient, public DoublyLinkedListNode<Canvas2DLayerBridge>, public RefCounted<Canvas2DLayerBridge> {
     WTF_MAKE_NONCOPYABLE(Canvas2DLayerBridge);
 public:
     enum OpacityMode {
         Opaque,
         NonOpaque
     };
 
-    static PassOwnPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D>, const IntSize&, OpacityMode);
+    static Canvas2DLayerBridgePtr create(PassRefPtr<GraphicsContext3D>, const IntSize&, OpacityMode);
 
     virtual ~Canvas2DLayerBridge();
 
     // WebKit::WebExternalTextureLayerClient implementation.
     virtual WebKit::WebGraphicsContext3D* context() OVERRIDE;
     virtual bool prepareMailbox(WebKit::WebExternalTextureMailbox*, WebKit::WebExternalBitmap*) OVERRIDE;
     virtual void mailboxReleased(const WebKit::WebExternalTextureMailbox&) OVERRIDE;
 
     // SkDeferredCanvas::NotificationClient implementation
     virtual void prepareForDraw() OVERRIDE;
     virtual void storageAllocatedForRecordingChanged(size_t) OVERRIDE;
     virtual void flushedDrawCommands() OVERRIDE;
     virtual void skippedPendingDrawCommands() OVERRIDE;
 
     // Methods used by Canvas2DLayerManager
     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;}
     void limitPendingFrames();
 
     WebKit::WebLayer* layer();
     void contextAcquired();
     SkCanvas* getCanvas() { return m_canvas; }
 
     unsigned backBufferTexture();
 
     bool isValid();
 
+    // Non-virtual overload of RefCounted::deref. RefPtr calls this one.

[Stephen White, 2013/08/23 14:45:28]

Nit: stale comment?

+    void destroy();
+
 protected:
     Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D>, SkDeferredCanvas*, OpacityMode);
     void setRateLimitingEnabled(bool);
+    bool isDead();

[Stephen White, 2013/08/23 14:45:28]

This doesn't seem to be defined anywhere.

 
     SkDeferredCanvas* m_canvas;
     OwnPtr<WebKit::WebExternalTextureLayer> m_layer;
     RefPtr<GraphicsContext3D> m_context;
     size_t m_bytesAllocated;
     bool m_didRecordDrawCommand;
     bool m_surfaceIsValid;
     int m_framesPending;
+    int m_liveMailboxCount;
+    bool m_destructionInProgress;
     bool m_rateLimitingEnabled;
 
     friend class WTF::DoublyLinkedListNode<Canvas2DLayerBridge>;
     Canvas2DLayerBridge* m_next;
     Canvas2DLayerBridge* m_prev;
 
     enum MailboxStatus {
         MailboxInUse,
         MailboxReleased,
         MailboxAvailable,
     };
 
     struct MailboxInfo {
         WebKit::WebExternalTextureMailbox m_mailbox;
         SkAutoTUnref<SkImage> m_image;
         MailboxStatus m_status;
+        RefPtr<Canvas2DLayerBridge> m_parentLayerBridge;
 
         MailboxInfo(const MailboxInfo&);
         MailboxInfo() {}
     };
     MailboxInfo* createMailboxInfo();
 
     uint32_t m_lastImageId;
     Vector<MailboxInfo> m_mailboxes;
 };
-
 }
-
 #endif