Exposes more mutation functions to MotionEventGeneric

ui/events/gesture_detection/motion_event_generic.h

Index: ui/events/gesture_detection/motion_event_generic.h
diff --git a/ui/events/gesture_detection/motion_event_generic.h b/ui/events/gesture_detection/motion_event_generic.h
index 9d7733fafd1a0d5d57aa42a6d7af14bc276ddd57..f12ec440a3083483ac89ff7521c686eaadf9c93c 100644
--- a/ui/events/gesture_detection/motion_event_generic.h
+++ b/ui/events/gesture_detection/motion_event_generic.h
@@ -70,7 +70,16 @@ class GESTURE_DETECTION_EXPORT MotionEventGeneric : public MotionEvent {
   float GetHistoricalY(size_t pointer_index,
                        size_t historical_index) const override;
 
-  void PushPointer(const PointerProperties& pointer);
+  // Adds |pointer| to the set of pointers returning the index it was added at.
+  size_t PushPointer(const PointerProperties& pointer);
+
+  // Removes the PointerProperties at |index|.
+  void RemovePointerAt(size_t index);
+
+  PointerProperties& pointer(size_t index) { return pointers_[index]; }
+  const PointerProperties& pointer(size_t index) const {
+    return pointers_[index];
+  }
 
   // Add an event to the history. |this| and |event| must have the same pointer
   // count and must both have an action of ACTION_MOVE.
@@ -93,11 +102,6 @@ class GESTURE_DETECTION_EXPORT MotionEventGeneric : public MotionEvent {
 
   void PopPointer();
 
-  PointerProperties& pointer(size_t index) { return pointers_[index]; }
-  const PointerProperties& pointer(size_t index) const {
-    return pointers_[index];
-  }
-
  private:
   enum { kTypicalMaxPointerCount = 5 };