Route OnDragEvent through ViewAndroid tree

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 1b219e8f840f813d8ad9d585e1b6caaccae2c4c5..7f013a967eeccf31e1e838c53d910e6f26022175 100644
--- a/ui/android/view_android.h
+++ b/ui/android/view_android.h
@@ -18,6 +18,7 @@ class Layer;
 }
 
 namespace ui {
+class DragEventAndroid;
 class EventForwarder;
 class MotionEventAndroid;
 class ViewClient;
@@ -63,7 +64,8 @@ class UI_ANDROID_EXPORT ViewAndroid {
   };
 
   // Layout parameters used to set the view's position and size.
-  // Position is in parent's coordinate space.
+  // Position is in parent's coordinate space, and all the values
+  // are in CSS pixel.
   struct LayoutParams {
     static LayoutParams MatchParent() { return {true, 0, 0, 0, 0}; }
     static LayoutParams Normal(int x, int y, int width, int height) {
@@ -158,25 +160,35 @@ class UI_ANDROID_EXPORT ViewAndroid {
   friend class EventForwarder;
   friend class ViewAndroidBoundsTest;
 
-  using ViewClientCallback =
-      const base::Callback<bool(ViewClient*, const MotionEventAndroid&)>;
-
+  bool OnDragEvent(const DragEventAndroid& event);
   bool OnTouchEvent(const MotionEventAndroid& event, bool for_touch_handle);
   bool OnMouseEvent(const MotionEventAndroid& event);
   bool OnMouseWheelEvent(const MotionEventAndroid& event);
 
   void RemoveChild(ViewAndroid* child);
 
-  bool HitTest(ViewClientCallback send_to_client,
-               const MotionEventAndroid& event);
+  template <typename E>
+  using ViewClientCallback =
+      const base::Callback<bool(ViewClient*, const E&, const gfx::PointF&)>;
+
+  template <typename E>
+  bool HitTest(ViewClientCallback<E> send_to_client,
+               const E& event,
+               const gfx::PointF& point);
 
+  static bool SendDragEventToClient(ViewClient* client,
+                                    const DragEventAndroid& event,
+                                    const gfx::PointF& point);
   static bool SendTouchEventToClient(bool for_touch_handle,
                                      ViewClient* client,
-                                     const MotionEventAndroid& event);
+                                     const MotionEventAndroid& event,
+                                     const gfx::PointF& point);
   static bool SendMouseEventToClient(ViewClient* client,
-                                     const MotionEventAndroid& event);
+                                     const MotionEventAndroid& event,
+                                     const gfx::PointF& point);
   static bool SendMouseWheelEventToClient(ViewClient* client,
-                                          const MotionEventAndroid& event);
+                                          const MotionEventAndroid& event,
+                                          const gfx::PointF& point);
 
   bool has_event_forwarder() const { return !!event_forwarder_; }