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

ui/aura/root_window.h

Index: ui/aura/root_window.h
diff --git a/ui/aura/root_window.h b/ui/aura/root_window.h
index 67498cfefbe2d7e4399cd8c1927674f71bd5e725..8c5f7e18c5e1d6d451ef31583547fb9ac94140c4 100644
--- a/ui/aura/root_window.h
+++ b/ui/aura/root_window.h
@@ -280,11 +280,11 @@ class AURA_EXPORT RootWindow : public ui::CompositorDelegate,
   // sending exited and entered events as its value changes.
   void HandleMouseMoved(const ui::MouseEvent& event, Window* target);
 
-  bool ProcessMouseEvent(Window* target, ui::MouseEvent* event);
-  bool ProcessKeyEvent(Window* target, ui::KeyEvent* event);
-  bool ProcessScrollEvent(Window* target, ui::ScrollEvent* event);
-  ui::EventResult ProcessTouchEvent(Window* target, ui::TouchEvent* event);
-  ui::EventResult ProcessGestureEvent(Window* target,
+  void ProcessMouseEvent(Window* target, ui::MouseEvent* event);
+  void ProcessKeyEvent(Window* target, ui::KeyEvent* event);
+  void ProcessScrollEvent(Window* target, ui::ScrollEvent* event);
+  void ProcessTouchEvent(Window* target, ui::TouchEvent* event);
+  void ProcessGestureEvent(Window* target,
                                       ui::GestureEvent* event);
   bool ProcessGestures(ui::GestureRecognizer::Gestures* gestures);