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

gpu/blink/webgraphicscontext3d_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_BLINK_WEBGRAPHICSCONTEXT3D_IMPL_H_
 #define GPU_BLINK_WEBGRAPHICSCONTEXT3D_IMPL_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 34 matching lines @@
                         ActiveInfo&) override;
 
   blink::WebString getProgramInfoLog(blink::WebGLId program) override;
   blink::WebString getShaderInfoLog(blink::WebGLId shader) override;
   blink::WebString getShaderSource(blink::WebGLId shader) override;
 
   blink::WebString getTranslatedShaderSourceANGLE(
       blink::WebGLId shader) override;
 
   void setContextLostCallback(
-      WebGraphicsContext3D::WebGraphicsContextLostCallback* callback) override;
+      WebGraphicsContext3D::WebGraphicsContextLostCallback* callback);
 
   void setErrorMessageCallback(
       WebGraphicsContext3D::WebGraphicsErrorMessageCallback* callback) override;
 
   // WebGraphicsContext3D implementation.
   ::gpu::gles2::GLES2Interface* getGLES2Interface() override;
 
   ::gpu::gles2::GLES2Interface* GetGLInterface() {
     return gl_;
   }
@@ skipping 28 matching lines @@
   // Errors raised by synthesizeGLError().
   std::vector<blink::WGC3Denum> synthetic_errors_;
 
   ::gpu::gles2::GLES2Interface* gl_;
   bool lose_context_when_out_of_memory_;
 };
 
 }  // namespace gpu_blink
 
 #endif  // GPU_BLINK_WEBGRAPHICSCONTEXT3D_IMPL_H_