IPC::ParamTraits for ui::Event (towards ui::Events over mojo IPC)

ui/events/gesture_event_details.h

Index: ui/events/gesture_event_details.h
diff --git a/ui/events/gesture_event_details.h b/ui/events/gesture_event_details.h
index ff88041fb3eeb38819000f8072b2624938f38aab..6a79a4ad1c12aa277a8078c880b7848e60d8ad7b 100644
--- a/ui/events/gesture_event_details.h
+++ b/ui/events/gesture_event_details.h
@@ -5,12 +5,18 @@
 #ifndef UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_
 
+#include <string.h>
+
 #include "base/logging.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/events_base_export.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
+namespace IPC {
+template <class P> struct ParamTraits;
+}
+
 namespace ui {
 
 struct EVENTS_BASE_EXPORT GestureEventDetails {
@@ -137,6 +143,14 @@ struct EVENTS_BASE_EXPORT GestureEventDetails {
     return data_.scroll_update.previous_update_in_sequence_prevented;
   }
 
+  // Supports comparison over internal structures for testing.
+  bool operator==(const GestureEventDetails& other) const {
+    return type_ == other.type_ &&
+           !memcmp(&data_, &other.data_, sizeof(Details)) &&
+           touch_points_ == other.touch_points_ &&
+           bounding_box_ == other.bounding_box_;
+  }
+
  private:
   EventType type_;
   union Details {
@@ -182,6 +196,10 @@ struct EVENTS_BASE_EXPORT GestureEventDetails {
     int tap_count;  // TAP repeat count.
   } data_;
 
+  // For mojo native implementation of (de)serialization.
+  friend struct IPC::ParamTraits<ui::GestureEventDetails>;
+  friend struct IPC::ParamTraits<ui::GestureEventDetails::Details>;
+
   int touch_points_;  // Number of active touch points in the gesture.
 
   // Bounding box is an axis-aligned rectangle that contains all the