Route OnDragEvent through ViewAndroid tree

ui/android/view_client.h

Index: ui/android/view_client.h
diff --git a/ui/android/view_client.h b/ui/android/view_client.h
index 99a87bb57113a162746c590b338c82a1a0ebfd4d..95bbc28401793f34180f7c988612c7f21e2bb34b 100644
--- a/ui/android/view_client.h
+++ b/ui/android/view_client.h
@@ -9,6 +9,7 @@
 
 namespace ui {
 
+class DragEventAndroid;
 class MotionEventAndroid;
 
 // Client interface used to forward events from Java to native views.
@@ -22,6 +23,7 @@ class UI_ANDROID_EXPORT ViewClient {
                             bool for_touch_handle);
   virtual bool OnMouseEvent(const MotionEventAndroid& event);
   virtual bool OnMouseWheelEvent(const MotionEventAndroid& event);
+  virtual bool OnDragEvent(const DragEventAndroid& event);
   virtual void OnPhysicalBackingSizeChanged();
 };