Enable WebGL rendering into ImageCHROMIUM, backed by a scanout buffer to enable overlay suppor…

Source/platform/graphics/gpu/DrawingBuffer.h

 /*
  * Copyright (c) 2010, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 52 matching lines @@
 public:
     virtual ~ContextEvictionManager() {};
 
     virtual void forciblyLoseOldestContext(const String& reason) = 0;
     virtual IntSize oldestContextSize() = 0;
 };
 
 // Manages a rendering target (framebuffer + attachment) for a canvas.  Can publish its rendering
 // results to a blink::WebLayer for compositing.
 class PLATFORM_EXPORT DrawingBuffer : public RefCounted<DrawingBuffer>, public blink::WebExternalTextureLayerClient  {
+    // If we used CHROMIUM_image as the backing storage for our buffers,
+    // we need to know the mapping from texture id to image.
+    struct TextureInfo {
+        Platform3DObject textureId;
+        blink::WGC3Duint imageId;
+
+        TextureInfo()
+            : textureId(0)
+            , imageId(0)
+        {
+        }
+    };
+
     struct MailboxInfo : public RefCounted<MailboxInfo> {
         blink::WebExternalTextureMailbox mailbox;
-        unsigned textureId;
+        TextureInfo textureInfo;
         IntSize size;
         // This keeps the parent drawing buffer alive as long as the compositor is
         // referring to one of the mailboxes DrawingBuffer produced. The parent drawing buffer is
         // cleared when the compositor returns the mailbox. See mailboxReleased().
         RefPtr<DrawingBuffer> m_parentDrawingBuffer;
     };
 public:
     enum PreserveDrawingBuffer {
         Preserve,
         Discard
@@ skipping 67 matching lines @@
         PassOwnPtr<blink::WebGraphicsContext3D>,
         PassOwnPtr<Extensions3DUtil>,
         bool multisampleExtensionSupported,
         bool packedDepthStencilExtensionSupported, PreserveDrawingBuffer, PassRefPtr<ContextEvictionManager>);
 
     bool initialize(const IntSize&);
 
 private:
     void mailboxReleasedWhileDestructionInProgress(const blink::WebExternalTextureMailbox&);
 
-    unsigned createColorTexture(const IntSize& size = IntSize());
+    unsigned createColorTexture();
     // Create the depth/stencil and multisample buffers, if needed.
     void createSecondaryBuffers();
     bool resizeFramebuffer(const IntSize&);
     bool resizeMultisampleFramebuffer(const IntSize&);
     void resizeDepthStencil(const IntSize&);
 
     // Bind to the m_framebufferBinding if it's not 0.
     void restoreFramebufferBinding();
 
     void clearPlatformLayer();
 
     PassRefPtr<MailboxInfo> recycledMailbox();
-    PassRefPtr<MailboxInfo> createNewMailbox(unsigned);
+    PassRefPtr<MailboxInfo> createNewMailbox(const TextureInfo&);
     void deleteMailbox(const blink::WebExternalTextureMailbox&);
 
     // Updates the current size of the buffer, ensuring that s_currentResourceUsePixels is updated.
     void setSize(const IntSize& size);
 
     // Calculates the difference in pixels between the current buffer size and the proposed size.
     static int pixelDelta(const IntSize& newSize, const IntSize& curSize);
 
     // Given the desired buffer size, provides the largest dimensions that will fit in the pixel budget
     // Returns true if the buffer will only fit if the oldest WebGL context is forcibly lost
@@ skipping 10 matching lines @@
     // Helper function which does a readback from the currently-bound
     // framebuffer into a buffer of a certain size with 4-byte pixels.
     void readBackFramebuffer(unsigned char* pixels, int width, int height, ReadbackOrder, WebGLImageConversion::AlphaOp);
 
     // Helper function to flip a bitmap vertically.
     void flipVertically(uint8_t* data, int width, int height);
 
     // Helper to texImage2D with pixel==0 case: pixels are initialized to 0.
     // By default, alignment is 4, the OpenGL default setting.
     void texImage2DResourceSafe(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, GLint alignment = 4);
+    // Allocate buffer storage to be sent to compositor using either texImage2D or CHROMIUM_image based on available support.
+    void allocateTextureMemory(TextureInfo*, const IntSize&);
+    void deleteChromiumImageForTexture(TextureInfo*);
 
     PreserveDrawingBuffer m_preserveDrawingBuffer;
     bool m_scissorEnabled;
     Platform3DObject m_texture2DBinding;
     Platform3DObject m_framebufferBinding;
     GLenum m_activeTextureUnit;
 
     OwnPtr<blink::WebGraphicsContext3D> m_context;
     OwnPtr<Extensions3DUtil> m_extensionsUtil;
     IntSize m_size;
     bool m_multisampleExtensionSupported;
     bool m_packedDepthStencilExtensionSupported;
     Platform3DObject m_fbo;
     // DrawingBuffer's output is double-buffered. m_colorBuffer is the back buffer.
-    Platform3DObject m_colorBuffer;
-    Platform3DObject m_frontColorBuffer;
+    TextureInfo m_colorBuffer;
+    TextureInfo m_frontColorBuffer;
 
     // This is used when we have OES_packed_depth_stencil.
     Platform3DObject m_depthStencilBuffer;
 
     // These are used when we don't.
     Platform3DObject m_depthBuffer;
     Platform3DObject m_stencilBuffer;
 
     // For multisampling.
     Platform3DObject m_multisampleFBO;
@@ skipping 39 matching lines @@
     // used to resize the Canvas.
     SkBitmap m_resizingBitmap;
 
     // Used to flip a bitmap vertically.
     Vector<uint8_t> m_scanline;
 };
 
 } // namespace WebCore
 
 #endif // DrawingBuffer_h