WebGL GL_RGB emulation to support IOSurfaces on Mac.

third_party/WebKit/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 140 matching lines @@
     GLuint framebuffer() const;
 
     bool discardFramebufferSupported() const { return m_discardFramebufferSupported; }
 
     void markContentsChanged();
     void setBufferClearNeeded(bool);
     bool bufferClearNeeded() const;
     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();
     gpu::gles2::GLES2Interface* contextGL();
     WebGraphicsContext3DProvider* contextProvider();
 
     // WebExternalTextureLayerClient implementation.
     bool prepareMailbox(WebExternalTextureMailbox*, WebExternalBitmap*) override;
     void mailboxReleased(const WebExternalTextureMailbox&, bool lostResource = false) override;
 
@@ skipping 114 matching lines @@
 
     // 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 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.
     TextureInfo createTextureAndAllocateMemory(const IntSize&);
 
     // Creates and allocates space for a default texture.
     TextureInfo createDefaultTextureAndAllocateMemory(const IntSize&);
 
     void resizeTextureMemory(TextureInfo*, const IntSize&);
 
@@ skipping 70 matching lines @@
     // used to resize the Canvas.
     SkBitmap m_resizingBitmap;
 
     // Used to flip a bitmap vertically.
     Vector<uint8_t> m_scanline;
 };
 
 } // namespace blink
 
 #endif // DrawingBuffer_h