egl/x11: Created a child window to control resizes and prevent flashes

ui/gl/gl_surface_egl.h

Index: ui/gl/gl_surface_egl.h
diff --git a/ui/gl/gl_surface_egl.h b/ui/gl/gl_surface_egl.h
index 8fb84a08003fedf5ef6cc01be500e5b8e406524b..2883e45c5b6937a8645b7989ec33dbb420b50fb7 100644
--- a/ui/gl/gl_surface_egl.h
+++ b/ui/gl/gl_surface_egl.h
@@ -98,18 +98,21 @@ class GL_EXPORT NativeViewGLSurfaceEGL : public GLSurfaceEGL {
   // Takes ownership of the VSyncProvider.
   virtual bool Initialize(scoped_ptr<VSyncProvider> sync_provider);
 
+  // Takes care of the platform dependant bits, of any, for creating the window.
+  virtual bool InitializeNativeWindow();
+
  protected:
   ~NativeViewGLSurfaceEGL() override;
 
   EGLNativeWindowType window_;
+  EGLConfig config_;
+  gfx::Size size_;
 
   void OnSetSwapInterval(int interval) override;
 
  private:
   EGLSurface surface_;
   bool supports_post_sub_buffer_;
-  EGLConfig config_;
-  gfx::Size size_;
 
   scoped_ptr<VSyncProvider> vsync_provider_;