Added Blink-side support for EXT_blend_minmax WebGL extension

Source/core/html/canvas/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 33 matching lines @@
 #include "wtf/OwnPtr.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 class WebLayer;
 }
 
 namespace WebCore {
 
 class ANGLEInstancedArrays;
+class EXTBlendMinMax;
 class EXTFragDepth;
 class EXTShaderTextureLOD;
 class EXTTextureFilterAnisotropic;
 class ExceptionState;
 class HTMLImageElement;
 class HTMLVideoElement;
 class ImageBuffer;
 class ImageData;
 class IntSize;
 class OESElementIndexUint;
@@ skipping 861 matching lines @@
     // If the vector is empty, return the maximum allowed active context number.
     static size_t oldestContextIndex();
     static IntSize oldestContextSize();
 };
 
 DEFINE_TYPE_CASTS(WebGLRenderingContextBase, CanvasRenderingContext, context, context->is3d(), context.is3d());
 
 } // namespace WebCore
 
 #endif // WebGLRenderingContextBase_h