Make lost context callback a base::Closure thru the WGC3DProvider.

third_party/WebKit/public/platform/WebGraphicsContext3D.h

 /*
  * Copyright (C) 2012 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 127 matching lines @@
 
     // The entry points below map directly to the OpenGL ES 2.0 API.
     // See: http://www.khronos.org/registry/gles/
     // and: http://www.khronos.org/opengles/sdk/docs/man/
     virtual bool getActiveAttrib(WebGLId program, WGC3Duint index, ActiveInfo&) = 0;
     virtual bool getActiveUniform(WebGLId program, WGC3Duint index, ActiveInfo&) = 0;
     virtual WebString getProgramInfoLog(WebGLId program) = 0;
     virtual WebString getShaderInfoLog(WebGLId shader) = 0;
     virtual WebString getShaderSource(WebGLId shader) = 0;
 
-    virtual void setContextLostCallback(WebGraphicsContextLostCallback* callback) { }
     virtual void setErrorMessageCallback(WebGraphicsErrorMessageCallback* callback) { }
 
     virtual WebString getTranslatedShaderSourceANGLE(WebGLId shader) = 0;
 
     // Prefer getting a GLES2Interface off WebGraphicsContext3DProvider if possible, and avoid using WebGraphicsContext3D at all.
     virtual gpu::gles2::GLES2Interface* getGLES2Interface() = 0;
 };
 
 } // namespace blink
 
 #endif