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

ui/base/events/event.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/base/events/event.h"
 
 #if defined(USE_X11)
 #include <X11/Xlib.h>
 #endif
 
@@ skipping 53 matching lines @@
     delete native_event_;
 #endif
 }
 
 bool Event::HasNativeEvent() const {
   base::NativeEvent null_event;
   std::memset(&null_event, 0, sizeof(null_event));
   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),
       flags_(flags),
       delete_native_event_(false),
       target_(NULL),
       phase_(EP_PREDISPATCH),
       result_(ER_UNHANDLED) {
   Init();
 }
@@ skipping 468 matching lines @@
 int GestureEvent::GetLowestTouchId() const {
   if (touch_ids_bitfield_ == 0)
     return -1;
   int i = -1;
   // Find the index of the least significant 1 bit
   while (!(1 << ++i & touch_ids_bitfield_));
   return i;
 }
 
 }  // namespace ui