arc: Fix mouse scroll on notification

ui/arc/notification/arc_custom_notification_view.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/arc/notification/arc_custom_notification_view.h"
 
 #include "components/exo/notification_surface.h"
 #include "components/exo/surface.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/base/l10n/l10n_util.h"
@@ skipping 22 matching lines @@
   // ui::EventHandler
   void OnEvent(ui::Event* event) override {
     // Do not forward event targeted to the floating close button so that
     // keyboard press and tap are handled properly.
     if (owner_->floating_close_button_widget_ && event->target() &&
         owner_->floating_close_button_widget_->GetNativeWindow() ==
             event->target()) {
       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_;
 
   DISALLOW_COPY_AND_ASSIGN(EventForwarder);
 };
 
 class ArcCustomNotificationView::SlideHelper
     : public ui::LayerAnimationObserver {
  public:
@@ skipping 265 matching lines @@
   } else if (!item_->pinned() && !floating_close_button_widget_) {
     CreateFloatingCloseButton();
   }
 }
 
 void ArcCustomNotificationView::OnItemNotificationSurfaceRemoved() {
   SetSurface(nullptr);
 }
 
 }  // namespace arc