Add EventForwarder for routing touch events

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 0abd77cdc40d55152a13aa423e46c79d90082f0c..84e4b167f03f04b7db6f178a06b76b7e8847645b 100644
--- a/ui/android/view_android.h
+++ b/ui/android/view_android.h
@@ -20,6 +20,9 @@ class Layer;
 
 namespace ui {
 
+class EventHandler;
+class MotionEventAndroid;
+class ViewClient;
 class WindowAndroid;
 
 // A simple container for a UI layer.
@@ -56,9 +59,7 @@ class UI_ANDROID_EXPORT ViewAndroid {
     // Default copy/assign disabled by move constructor.
   };
 
-  // A ViewAndroid may have its own delegate or otherwise will
-  // use the next available parent's delegate.
-  ViewAndroid(const base::android::JavaRef<jobject>& delegate);
+  explicit ViewAndroid(ViewClient* view_client);
 
   ViewAndroid();
   virtual ~ViewAndroid();
@@ -83,7 +84,11 @@ class UI_ANDROID_EXPORT ViewAndroid {
 
   void SetDelegate(const base::android::JavaRef<jobject>& delegate);
 
-  // Adds this view as a child of another view.
+  // Creates |EventHandler| for a view tree below (not including) WindowAndroid.
+  // Only one instance per the view tree is allowed at its top VA.
+  EventHandler* CreateEventHandler();
+
+  // Adds a child to this view.
   void AddChild(ViewAndroid* child);
 
   // Detaches this view from its parent.
@@ -106,12 +111,23 @@ class UI_ANDROID_EXPORT ViewAndroid {
   // This may return null.
   base::android::ScopedJavaLocalRef<jobject> GetContainerView();
 
+  bool OnTouchEvent(const MotionEventAndroid& event,
+                    bool is_touch_handle_event);
+  bool OnMouseEvent(const MotionEventAndroid& event, int action_button);
+
+  // Virtual for testing.
+  virtual float GetDipScale();
+
  protected:
   ViewAndroid* parent_;
 
  private:
   void RemoveChild(ViewAndroid* child);
 
+  bool has_event_handler() const { return !!event_handler_; }
+
+  static bool ViewTreeHasEventHandler(ViewAndroid* view);
+
   // Returns the Java delegate for this view. This is used to delegate work
   // up to the embedding view (or the embedder that can deal with the
   // implementation details).
@@ -121,7 +137,12 @@ class UI_ANDROID_EXPORT ViewAndroid {
   std::list<ViewAndroid*> children_;
   scoped_refptr<cc::Layer> layer_;
   JavaObjectWeakGlobalRef delegate_;
-  gfx::Vector2dF content_offset_;  // in CSS pixel
+
+  ViewClient* const client_;
+
+  gfx::Vector2dF content_offset_;  // in CSS pixel.
+  std::unique_ptr<EventHandler> event_handler_;
+  float dip_scale_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewAndroid);
 };