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..f889e0d88a7bf921cff09e9a58074340b3340d26 100644
--- a/ui/events/gesture_event_details.h
+++ b/ui/events/gesture_event_details.h
@@ -5,7 +5,10 @@
 #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 "ipc/ipc_message_utils.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/events_base_export.h"
 #include "ui/gfx/geometry/rect.h"
@@ -182,11 +185,24 @@ 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
   // enclosing rectangles of the touch-points in the gesture.
   gfx::RectF bounding_box_;
+
+ public:
+  // Supports comparison over internal structures for testing.
+  bool operator==(const GestureEventDetails& other) const {

[Ken Rockot(use gerrit already), 2016/02/17 22:05:21]

Maybe it would be better to expose something like IsEqualForTesting if you
actually want this to be used in testing only.

[Mark Dittmer, 2016/02/18 14:51:05]

Could do. There are two reasons I prefer implementing ==

(1) This really is what's meant by equality for this type (perhaps this
assertion betrays the comment above).
(2) IMHO, we get more readable test code and test code output being able to
ASSERT_EQ(ged1, ged2).

If it better follows our operator-impl + testing idioms to follow your
suggestion, feel free to push back and I'll change it.

+    return type_ == other.type_ &&
+           !memcmp(&data_, &other.data_, sizeof(Details)) &&
+           touch_points_ == other.touch_points_ &&
+           bounding_box_ == other.bounding_box_;
+  }
 };
 
 }  // namespace ui