Add multi-finger swipe detection to GestureDetector

ui/events/gesture_detection/gesture_provider.h

 // Copyright 2014 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.
 
 #ifndef UI_EVENTS_GESTURE_DETECTION_GESTURE_PROVIDER_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_PROVIDER_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
@@ skipping 25 matching lines @@
 
     // If |disable_click_delay| is true and double-tap support is disabled,
     // there will be no delay before tap events. When double-tap support is
     // enabled, there will always be a delay before a tap event is fired, in
     // order to allow the double tap gesture to occur without firing any tap
     // events.
     bool disable_click_delay;
 
     // If |gesture_begin_end_types_enabled| is true, fire an ET_GESTURE_BEGIN
     // event for every added touch point, and an ET_GESTURE_END event for every
-    // removed touch point.
+    // removed touch point. Defaults to false.
     bool gesture_begin_end_types_enabled;
   };
 
   GestureProvider(const Config& config, GestureProviderClient* client);
   ~GestureProvider();
 
   // Handle the incoming MotionEvent, returning false if the event could not
   // be handled.
   bool OnTouchEvent(const MotionEvent& event);
 
@@ skipping 63 matching lines @@
   // opened after a GESTURE_LONG_PRESS, this is used to insert a
   // GESTURE_TAP_CANCEL for removing any ::active styling.
   base::TimeTicks current_longpress_time_;
 
   bool gesture_begin_end_types_enabled_;
 };
 
 }  //  namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_PROVIDER_H_