events: Start changing EventHandler interface to not return a value.

ui/base/events/event.cc

Index: ui/base/events/event.cc
diff --git a/ui/base/events/event.cc b/ui/base/events/event.cc
index 4658e46cb92caf76929c672c916b91d5a2dc4996..c8399d81fb3dc4d06c99bb4e1eadbfd62dc448e7 100644
--- a/ui/base/events/event.cc
+++ b/ui/base/events/event.cc
@@ -71,6 +71,17 @@ bool Event::HasNativeEvent() const {
   return !!std::memcmp(&native_event_, &null_event, sizeof(null_event));
 }
 
+void Event::StopPropagation() {
+  CHECK(phase_ != EP_PREDISPATCH && phase_ != EP_POSTDISPATCH);
+  result_ = static_cast<ui::EventResult>(result_ | ER_CONSUMED);
+  CHECK(stopped_propagation());
+}
+
+void Event::PreventDefault() {
+  CHECK(phase_ != EP_PREDISPATCH && phase_ != EP_POSTDISPATCH);

[Ben Goodger (Google), 2012/12/03 17:36:54]

i would also like the ability to prevent this (and probably stoppropagation?)
via a flag on the dispatcher api to event. e.g. focus change events should not
be cancelable.

can be done in a followon cl.

[sadrul, 2012/12/03 17:45:20]

Indeed. I have that in mind :) [ crbug.com/163617 ]

+  result_ = static_cast<ui::EventResult>(result_ | ER_HANDLED);
+}
+
 Event::Event(EventType type, base::TimeDelta time_stamp, int flags)
     : type_(type),
       time_stamp_(time_stamp),