WebGL GL_RGB emulation to support IOSurfaces on Mac.

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
index 4d1e7bed0b4aca88899abb49ee5e8d63e603672b..9e95a17e84e2dda59096f6f5c8e752ae31f8fc72 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
@@ -143,6 +143,14 @@ public:
         }
     }
 
+    // The DrawingBuffer needs to track the currently bound renderbuffer so it
+    // restore the binding when needed.
+    void setRenderbufferBinding(GLuint renderbuffer)
+    {
+        m_renderbufferBinding = renderbuffer;
+    }
+
+
     // Track the currently active texture unit. Texture unit 0 is used as host for a scratch
     // texture.
     void setActiveTextureUnit(GLint textureUnit) { m_activeTextureUnit = textureUnit; }
@@ -159,6 +167,12 @@ public:
     void setIsHidden(bool);
     void setFilterQuality(SkFilterQuality);
 
+    // Indicates that the currently bound framebuffer has internalformat
+    // GL_RGBA, but is emulating GL_RGB. This happens to the backbuffer when the
+    // client requests alpha:False, but GL_RGB textures are unusable because of
+    // driver bugs.
+    bool requiresRGBEmulation();
+
     WebLayer* platformLayer();
 
     WebGraphicsContext3D* context();
@@ -202,12 +216,18 @@ private:
         DISALLOW_NEW();
         GLenum target;
         GLenum internalColorFormat;
+
+        // The internal color format used when allocating storage for the
+        // texture. This may be different from internalColorFormat if RGB
+        // emulation is required.
+        GLenum creationInternalColorFormat;
         GLenum colorFormat;
         GLenum internalRenderbufferFormat;
 
         TextureParameters()
             : target(0)
             , internalColorFormat(0)
+            , creationInternalColorFormat(0)
             , colorFormat(0)
             , internalRenderbufferFormat(0)
         {
@@ -293,6 +313,10 @@ private:
     // Allocate buffer storage to be sent to compositor using either texImage2D or CHROMIUM_image based on available support.
     void deleteChromiumImageForTexture(TextureInfo*);
 
+    // If RGB emulation is required, then the CHROMIUM image must be immediately
+    // cleared after it is bound to a texture.
+    void clearChromiumImageIfNecessary(const TextureInfo&);
+
     // Tries to create a CHROMIUM_image backed texture if
     // RuntimeEnabledFeatures::webGLImageChromiumEnabled() is true. On failure,
     // or if the flag is false, creates a default texture.
@@ -310,6 +334,7 @@ private:
     GLuint m_texture2DBinding;
     GLuint m_drawFramebufferBinding;
     GLuint m_readFramebufferBinding;
+    GLuint m_renderbufferBinding;
     GLenum m_activeTextureUnit;
 
     OwnPtr<WebGraphicsContext3DProvider> m_contextProvider;
@@ -337,6 +362,8 @@ private:
 
     // For multisampling.
     GLuint m_multisampleFBO;
+    GLuint m_multisampleIntermediateFBO;
+    GLuint m_multisampleIntermediateRenderbuffer;
     GLuint m_multisampleColorBuffer;
 
     // True if our contents have been modified since the last presentation of this buffer.