Store physical backing size in ViewAndroid

ui/android/view_android.h

Index: ui/android/view_android.h
diff --git a/ui/android/view_android.h b/ui/android/view_android.h
index fbd3c452cd1bfc555b5e50c828b7d4f2ad255c22..8efe1b6a65748887a5317dabe5c96f62c2157b79 100644
--- a/ui/android/view_android.h
+++ b/ui/android/view_android.h
@@ -133,6 +133,8 @@ class UI_ANDROID_EXPORT ViewAndroid {
   bool StartDragAndDrop(const base::android::JavaRef<jstring>& jtext,
                         const base::android::JavaRef<jobject>& jimage);
 
+  gfx::Size GetPhysicalBackingSize();
+  void OnPhysicalBackingSizeChanged(const gfx::Size& size);
   void OnBackgroundColorChanged(unsigned int color);
   void OnTopControlsChanged(float top_controls_offset,
                             float top_content_offset);
@@ -201,6 +203,8 @@ class UI_ANDROID_EXPORT ViewAndroid {
   // the passed events should be processed by the view.
   LayoutParams layout_params_;
 
+  gfx::Size physical_size_;
+
   gfx::Vector2dF content_offset_;  // in CSS pixel.
   std::unique_ptr<EventForwarder> event_forwarder_;