arc: Fix mouse scroll on notification

ui/arc/notification/arc_custom_notification_view.cc

Index: ui/arc/notification/arc_custom_notification_view.cc
diff --git a/ui/arc/notification/arc_custom_notification_view.cc b/ui/arc/notification/arc_custom_notification_view.cc
index b17c2344b27f5c27eac41b543205558d04edd53c..a44364356e0ff83360a31cb8a8017de442c91c3e 100644
--- a/ui/arc/notification/arc_custom_notification_view.cc
+++ b/ui/arc/notification/arc_custom_notification_view.cc
@@ -40,7 +40,30 @@ class ArcCustomNotificationView::EventForwarder : public ui::EventHandler {
       return;
     }
 
-    owner_->OnEvent(event);
+    if (event->IsScrollEvent())
+      ForwardScrollEvent(event->AsScrollEvent());
+    else if (event->IsMouseWheelEvent())
+      ForwardMouseWheelEvent(event->AsMouseWheelEvent());
+    else if (!event->IsTouchEvent())

[yoshiki, 2016/08/31 18:04:37]

nit: as we discussed in chat, please add a comment of why you're skipping only
touch event.

[xiyuan, 2016/08/31 18:08:23]

Done.

+      owner_->OnEvent(event);
+  }
+
+  void ForwardScrollEvent(ui::ScrollEvent* event) {
+    views::Widget* widget = owner_->GetWidget();
+    if (!widget)
+      return;
+
+    event->target()->ConvertEventToTarget(widget->GetNativeWindow(), event);
+    widget->OnScrollEvent(event);
+  }
+
+  void ForwardMouseWheelEvent(ui::MouseWheelEvent* event) {
+    views::Widget* widget = owner_->GetWidget();
+    if (!widget)
+      return;
+
+    event->target()->ConvertEventToTarget(widget->GetNativeWindow(), event);
+    widget->OnMouseEvent(event);
   }
 
   ArcCustomNotificationView* const owner_;