[Android] Select text when stylus first button is pressed.

ui/events/gesture_detection/motion_event.h

Index: ui/events/gesture_detection/motion_event.h
diff --git a/ui/events/gesture_detection/motion_event.h b/ui/events/gesture_detection/motion_event.h
index 899aeea1c2ae7b8530cfbb1af15e57824bb2b29d..764956b1334d504dd0a748b6e2d0698f9a81f6f7 100644
--- a/ui/events/gesture_detection/motion_event.h
+++ b/ui/events/gesture_detection/motion_event.h
@@ -53,6 +53,8 @@ class GESTURE_DETECTION_EXPORT MotionEvent {
                                size_t historical_index) const = 0;
   virtual float GetHistoricalY(size_t pointer_index,
                                size_t historical_index) const = 0;
+  virtual int GetSource() const = 0;
+  virtual int GetButtonState() const = 0;
 
   virtual scoped_ptr<MotionEvent> Clone() const = 0;
   virtual scoped_ptr<MotionEvent> Cancel() const = 0;