Add AcceleratorType to EventMatcher

components/mus/public/interfaces/input_event_constants.mojom

Index: components/mus/public/interfaces/input_event_constants.mojom
diff --git a/components/mus/public/interfaces/input_event_constants.mojom b/components/mus/public/interfaces/input_event_constants.mojom
index 03bd80bd342d8ba2d7ae5b57c426cd705ed5cacc..3c2d6d61ab85facc49058e1cc1430883e431752e 100644
--- a/components/mus/public/interfaces/input_event_constants.mojom
+++ b/components/mus/public/interfaces/input_event_constants.mojom
@@ -4,6 +4,15 @@
 
 module mus.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.
+enum AcceleratorPhase {
+  PRE_TARGET,
+  POST_TARGET,
+};
+
 enum EventType {
   UNKNOWN,
   KEY_PRESSED,