Support 3f swipe for tab scrubbing

ui/base/events/event.h

 // 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.
 
 #ifndef UI_BASE_EVENTS_EVENT_H_
 #define UI_BASE_EVENTS_EVENT_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/event_types.h"
@@ skipping 563 matching lines @@
  public:
   explicit ScrollEvent(const base::NativeEvent& native_event);
   template <class T>
   ScrollEvent(const ScrollEvent& model,
               T* source,
               T* target,
               EventType type,
               int flags)
       : MouseEvent(model, source, target, type, flags),
         x_offset_(model.x_offset_),
-        y_offset_(model.y_offset_) {
+        y_offset_(model.y_offset_),
+        finger_count_(model.finger_count_){
   }
 
   // Used for tests.
   ScrollEvent(EventType type,
               const gfx::Point& location,
               int flags,
               float x_offset,
               float y_offset);
 
   float x_offset() const { return x_offset_; }
   float y_offset() const { return y_offset_; }
+  int finger_count() const { return finger_count_; }
 
  private:
   float x_offset_;
   float y_offset_;
+  int finger_count_;
 
   DISALLOW_COPY_AND_ASSIGN(ScrollEvent);
 };
 
 class UI_EXPORT GestureEvent : public LocatedEvent {
  public:
   GestureEvent(EventType type,
                int x,
                int y,
                int flags,
@@ skipping 27 matching lines @@
   // This value is stored as a bitfield because the number of touch ids varies,
   // but we currently don't need more than 32 touches at a time.
   const unsigned int touch_ids_bitfield_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureEvent);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_EVENTS_EVENT_H_