events: Clean up dispatching code for touch-events.

ui/base/events/event_constants.h

Index: ui/base/events/event_constants.h
diff --git a/ui/base/events/event_constants.h b/ui/base/events/event_constants.h
index 6785633f7782ae5ca5515b4f88121a4bd277ec09..ee2e2461901989cfc7c93bfabe8fed25f292b5e9 100644
--- a/ui/base/events/event_constants.h
+++ b/ui/base/events/event_constants.h
@@ -98,12 +98,14 @@ enum MouseEventFlags {
 
 // Result of dispatching an event.
 enum EventResult {
-  ER_UNHANDLED = 0,  // The event hasn't been handled. The event can be
-                     // propagated to other handlers.
-  ER_HANDLED,        // The event has already been handled, but it can still be
-                     // propagated to other handlers.
-  ER_CONSUMED,       // The event has been handled, and it should not be
-                     // propagated to other handlers.
+  ER_UNHANDLED = 0,       // The event hasn't been handled. The event can be
+                          // propagated to other handlers.
+  ER_HANDLED   = 1 << 0,  // The event has already been handled, but it can
+                          // still be propagated to other handlers.
+  ER_CONSUMED  = 1 << 1,  // The event has been handled, and it should not be
+                          // propagated to other handlers.
+  ER_ASYNC     = 1 << 2,  // The event will be processed asynchronously. The

[Ben Goodger (Google), 2012/09/26 19:42:48]

Can you tell me how 'asynchronously' works and what this return code would be
interpreted by the caller?

[sadrul, 2012/09/26 21:26:05]

Right now, ASYNC is only used for touch-events, and this is returned only by
RenderWidgetHostViewAura. (I don't think there will be any other places that
will do this in the future)

For each touch-event that is processed as ASYNC, the RootWindow adds it in a
queue in the GestureRecognizer. For each such ASYNC touch event, the RWHVA calls
RootWindow::AdvanceQueuedTouchEvent asynchronously (after it receives an ACK
from renderer/WebKit). At this point, the GR removes the event from the queue
and processes it (and may generate gesture events, which are then dispatched by
the RootWindow).

There is plan to move the touch-event queue out of the GR and into content/,
since that will allow other platforms (e.g. android) to use the same queueing
code: crbug.com/138153. Once that happens, this ER_SYNC will no longer be
necessary.

+                          // event can still be propagated to other handlers.
 };
 
 // Phase of the event dispatch.
@@ -122,9 +124,6 @@ enum TouchStatus {
   TOUCH_STATUS_CONTINUE,     // The touch event is part of a previously
                              // started touch sequence.
   TOUCH_STATUS_END,          // The touch event ended the touch sequence.
-  TOUCH_STATUS_SYNTH_MOUSE,  // The touch event was not processed, but a
-                             // synthetic mouse event generated from the
-                             // unused touch event was handled.
   TOUCH_STATUS_QUEUED,       // The touch event has not been processed yet, but
                              // may be processed asynchronously later. This also
                              // places a lock on touch-events (i.e. all