Adds ability for pre-target accelerators to not consume events

ui/events/mojo/event_constants.mojom

Index: ui/events/mojo/event_constants.mojom
diff --git a/ui/events/mojo/event_constants.mojom b/ui/events/mojo/event_constants.mojom
index 445cffbade6c7bc45755ede8f25e6898ad210201..6ad8d67e1f37954a36ffd47e38fe095cb7b7d617 100644
--- a/ui/events/mojo/event_constants.mojom
+++ b/ui/events/mojo/event_constants.mojom
@@ -4,10 +4,9 @@
 
 module ui.mojom;
 
-// Denotes during which phase of event targeting that an accelerator will be
-// notified of an event. PRE_TARGET will be notified instead of the target
-// window. POST_TARGET will be notified after the target window, and only if the
-// event was not consumed by the target.
+// AcceleratorPhase specifies which phase of event matching the matcher should
+// be considered for. See WindowTree for details on how it handles the
+// AcceleratorPhase.
 enum AcceleratorPhase {
   PRE_TARGET,
   POST_TARGET,