Avoid heap allocations with GestureEventDataPacket

ui/events/gesture_detection/gesture_event_data_packet.h

Index: ui/events/gesture_detection/gesture_event_data_packet.h
diff --git a/ui/events/gesture_detection/gesture_event_data_packet.h b/ui/events/gesture_detection/gesture_event_data_packet.h
index 0c40f5767849c1bbea4a69c05df9286f1998c106..9b115de9ca77b29c2210b4933cd9a78acbb69198 100644
--- a/ui/events/gesture_detection/gesture_event_data_packet.h
+++ b/ui/events/gesture_detection/gesture_event_data_packet.h
@@ -5,8 +5,7 @@
 #ifndef UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DATA_PACKET_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DATA_PACKET_H_
 
-#include <vector>
-
+#include "base/containers/stack_container.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
 #include "ui/events/gesture_detection/gesture_event_data.h"
 
@@ -44,7 +43,7 @@ class GESTURE_DETECTION_EXPORT GestureEventDataPacket {
 
   const base::TimeTicks& timestamp() const { return timestamp_; }
   const GestureEventData& gesture(size_t i) const { return gestures_[i]; }
-  size_t gesture_count() const { return gestures_.size(); }
+  size_t gesture_count() const { return gestures_->size(); }
   GestureSource gesture_source() const { return gesture_source_; }
   const gfx::PointF& touch_location() const { return touch_location_; }
   const gfx::PointF& raw_touch_location() const { return raw_touch_location_; }
@@ -55,9 +54,9 @@ class GESTURE_DETECTION_EXPORT GestureEventDataPacket {
                          const gfx::PointF& touch_location,
                          const gfx::PointF& raw_touch_location);
 
+  enum { kTypicalMaxGesturesPerTouch = 5 };
   base::TimeTicks timestamp_;
-  // TODO(jdduke): This vector is in general very short. Optimize?
-  std::vector<GestureEventData> gestures_;
+  base::StackVector<GestureEventData, kTypicalMaxGesturesPerTouch> gestures_;
   gfx::PointF touch_location_;
   gfx::PointF raw_touch_location_;
   GestureSource gesture_source_;