WebGL GL_RGB emulation to support IOSurfaces on Mac.

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h

 /*
  * Copyright (C) 2009 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 120 matching lines @@
         // Restore DrawingBuffer if needed
         if (!m_readFramebufferBinding && m_drawingBuffer)
             m_drawingBuffer->restoreFramebufferBindings();
     }
 
 private:
     DrawingBuffer* m_drawingBuffer;
     Member<WebGLFramebuffer> m_readFramebufferBinding;
 };
 
+// This class uses the color mask to prevents drawing to the alpha channel, if

[Ken Russell (switch to Gerrit), 2016/05/03 23:32:27]

typo: prevents -> prevent

[erikchen, 2016/05/04 00:23:11]

Done.

+// the DrawingBuffer requires RGB emulation.
+class ScopedRGBEmulationColorMask {
+public:
+    ScopedRGBEmulationColorMask(gpu::gles2::GLES2Interface*, GLboolean* colorMask, DrawingBuffer*);
+    ~ScopedRGBEmulationColorMask();
+
+private:
+    gpu::gles2::GLES2Interface* m_contextGL;
+    GLboolean m_colorMask[4];
+    const bool m_requiresEmulation;
+};
+
 class MODULES_EXPORT WebGLRenderingContextBase : public CanvasRenderingContext {
 public:
     ~WebGLRenderingContextBase() override;
 
     virtual unsigned version() const = 0;
     virtual String contextName() const = 0;
     virtual void registerContextExtensions() = 0;
 
     virtual void initializeNewContext();
 
@@ skipping 928 matching lines @@
     WebGLRenderingContextBase(HTMLCanvasElement*, OffscreenCanvas*, PassOwnPtr<WebGraphicsContext3DProvider>, const WebGLContextAttributes&);
 };
 
 DEFINE_TYPE_CASTS(WebGLRenderingContextBase, CanvasRenderingContext, context, context->is3d(), context.is3d());
 
 } // namespace blink
 
 WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(blink::WebGLRenderingContextBase::TextureUnitState);
 
 #endif // WebGLRenderingContextBase_h