Android: Use virtualized context only for those with compatible config

ui/gl/gl_surface_osmesa.h

Index: ui/gl/gl_surface_osmesa.h
diff --git a/ui/gl/gl_surface_osmesa.h b/ui/gl/gl_surface_osmesa.h
index 6c317ea3e92146fd1eee668e7d4581713014b255..7a7fa3c0fdf654fbefd2bcfcc8af9d28b59ada00 100644
--- a/ui/gl/gl_surface_osmesa.h
+++ b/ui/gl/gl_surface_osmesa.h
@@ -33,13 +33,12 @@ class GL_EXPORT GLSurfaceOSMesa : public GLSurface {
   gfx::SwapResult SwapBuffers() override;
   gfx::Size GetSize() override;
   void* GetHandle() override;
-  unsigned GetFormat() override;
+  GLSurface::Format GetFormat() override;
 
  protected:
   ~GLSurfaceOSMesa() override;
 
  private:
-  unsigned format_;
   gfx::Size size_;
   scoped_ptr<int32_t[]> buffer_;