Fix app icon issue after long press in folder

Background:
Long press on app icon in folder will enlarge the icon, but release will
not reset it. The long press gesture event is not handled by
AppListItemView, thus passed to AppsGridView which handles it. The
gesture end event will thus be sent to AppsGridView directly without
going through AppListItemView. This is caused by go/cgcl/987293

Change:
Only handle the scroll begin event in AppsGridView if in folder instead
of all gesture events.

BUG=830982

Change-Id: I2ca5bddaf22cd198d6e9cca5ee5f04c9798153e8
Reviewed-on: https://chromium-review.googlesource.com/1008906Reviewed-by: Yury Khmel <khmel@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551023}

ui/app_list/views/apps_grid_view.cc

@@ -911,11 +911,11 @@ void AppsGridView::OnGestureEvent(ui::GestureEvent* event) {
     return;
   }
 
-  // Gesture events should not be passed to ancestor views if it occurs inside
-  // the folder bounds even it is not handled. This prevents user from closing
-  // the folder when scrolling inside it.
+  // Scroll begin events should not be passed to ancestor views if it occurs
+  // inside the folder bounds even it is not handled. This prevents user from
+  // closing the folder when scrolling inside it.
   if (pagination_controller_->OnGestureEvent(*event, GetContentsBounds()) ||
-      folder_delegate_) {
+      (folder_delegate_ && event->type() == ui::ET_GESTURE_SCROLL_BEGIN)) {
     event->SetHandled();
   }
 }