command_buffer_gles2: Implement EGL default Display as a global object

gpu/command_buffer/service/gles2_cmd_decoder.h

Index: gpu/command_buffer/service/gles2_cmd_decoder.h
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.h b/gpu/command_buffer/service/gles2_cmd_decoder.h
index 8565a516b8fe560b1287f96934f8289b8bd544d1..0335df74c53f8929aacb871d7b56893acbf95fdf 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.h
@@ -158,6 +158,9 @@ class GPU_EXPORT GLES2Decoder : public base::SupportsWeakPtr<GLES2Decoder>,
 
   // Set the surface associated with the default FBO.
   virtual void SetSurface(const scoped_refptr<gfx::GLSurface>& surface) = 0;
+  // Releases the surface associated with the GL context.
+  // The decoder should not be used until a new surface is set.
+  virtual void ReleaseSurface() = 0;
 
   virtual void ProduceFrontBuffer(const Mailbox& mailbox) = 0;