gestures: Generate only either scroll-end or fling-start events at the end of a scroll gesture.

ui/app_list/contents_view.cc

 // Copyright (c) 2012 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/app_list/contents_view.h"
 
 #include <algorithm>
 
 #include "ui/app_list/app_list_view.h"
 #include "ui/app_list/apps_grid_view.h"
@@ skipping 186 matching lines @@
     case ui::ET_GESTURE_SCROLL_UPDATE:
       // event.details.scroll_x() > 0 means moving contents to right. That is,
       // transitioning to previous page.
       pagination_model_->UpdateScroll(
           event.details().scroll_x() / GetContentsBounds().width());
       return ui::GESTURE_STATUS_CONSUMED;
     case ui::ET_GESTURE_SCROLL_END:
       pagination_model_->EndScroll();
       return ui::GESTURE_STATUS_CONSUMED;
     case ui::ET_SCROLL_FLING_START: {
+      pagination_model_->EndScroll();
       if (fabs(event.details().velocity_x()) > kMinHorizVelocityToSwitchPage) {
+        pagination_model_->ResetTransitionAnimation();
         pagination_model_->SelectPageRelative(
             event.details().velocity_x() < 0 ? 1 : -1,
             true);
-        return ui::GESTURE_STATUS_CONSUMED;
       }
-      break;
+      return ui::GESTURE_STATUS_CONSUMED;
     }
     default:
       break;
   }
 
   return ui::GESTURE_STATUS_UNKNOWN;
 }
 
 bool ContentsView::OnKeyPressed(const views::KeyEvent& event) {
   switch (show_state_) {
@@ skipping 29 matching lines @@
       pagination_model_->SelectPageRelative(event.x_offset() > 0 ? 1 : -1,
                                             true);
     }
     return true;
   }
 
   return false;
 }
 
 }  // namespace app_list