Store the id of a contributing motion event in GestureEventData

content/browser/renderer_host/input/motion_event_android.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 CONTENT_BROWSER_RENDERER_HOST_INPUT_MOTION_EVENT_ANDROID_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_MOTION_EVENT_ANDROID_H_
 
 #include <jni.h>
 
 #include "base/android/scoped_java_ref.h"
@@ skipping 20 matching lines @@
                      jfloat pos_y_0,
                      jfloat pos_x_1,
                      jfloat pos_y_1,
                      jint pointer_id_0,
                      jint pointer_id_1,
                      jfloat touch_major_0,
                      jfloat touch_major_1);
   virtual ~MotionEventAndroid();
 
   // ui::MotionEvent methods.
+  virtual int GetId() const OVERRIDE;
   virtual Action GetAction() const OVERRIDE;
   virtual int GetActionIndex() const OVERRIDE;
   virtual size_t GetPointerCount() const OVERRIDE;
   virtual int GetPointerId(size_t pointer_index) const OVERRIDE;
   virtual float GetX(size_t pointer_index) const OVERRIDE;
   virtual float GetY(size_t pointer_index) const OVERRIDE;
   virtual float GetTouchMajor(size_t pointer_index) const OVERRIDE;
   virtual float GetPressure(size_t pointer_index) const OVERRIDE;
   virtual base::TimeTicks GetEventTime() const OVERRIDE;
   virtual size_t GetHistorySize() const OVERRIDE;
@@ skipping 52 matching lines @@
   float cached_touch_majors_[MAX_POINTERS_TO_CACHE];
 
   // Whether |event_| should be recycled on destruction. This will only be true
   // for those events generated via |Obtain(...)|.
   bool should_recycle_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_MOTION_EVENT_ANDROID_H_