Adds ability for pre-target accelerators to not consume events

services/ui/ws/event_dispatcher.h

Index: services/ui/ws/event_dispatcher.h
diff --git a/services/ui/ws/event_dispatcher.h b/services/ui/ws/event_dispatcher.h
index 8d0ca2919ccff37d9c9dac6def55fa7819e483a8..a3f3dd77b18087dfc4c9b0f0f5d3164fbdf76a0a 100644
--- a/services/ui/ws/event_dispatcher.h
+++ b/services/ui/ws/event_dispatcher.h
@@ -38,6 +38,15 @@ class EventDispatcherTestApi;
 // Handles dispatching events to the right location as well as updating focus.
 class EventDispatcher : public ServerWindowObserver {
  public:
+  enum class AcceleratorMatchPhase {
+    // Both pre and post should be considered.
+    ANY,
+
+    // PRE_TARGETs are not considered, only the actual target and any
+    // accelerators registered with POST_TARGET.
+    POST_ONLY,
+  };
+
   explicit EventDispatcher(EventDispatcherDelegate* delegate);
   ~EventDispatcher() override;
 
@@ -104,8 +113,11 @@ class EventDispatcher : public ServerWindowObserver {
   void RemoveAccelerator(uint32_t id);
 
   // Processes the supplied event, informing the delegate as approriate. This
-  // may result in generating any number of events.
-  void ProcessEvent(const ui::Event& event);
+  // may result in generating any number of events. If |match_phase| is
+  // ANY and there is a matching accelerator with PRE_TARGET found, than only
+  // OnAccelerator() is called. The expectation is after the PRE_TARGET has been
+  // handled this is again called with an AcceleratorMatchPhase of POST_ONLY.
+  void ProcessEvent(const ui::Event& event, AcceleratorMatchPhase match_phase);
 
  private:
   friend class test::EventDispatcherTestApi;
@@ -130,7 +142,8 @@ class EventDispatcher : public ServerWindowObserver {
     bool is_pointer_down;
   };
 
-  void ProcessKeyEvent(const ui::KeyEvent& event);
+  void ProcessKeyEvent(const ui::KeyEvent& event,
+                       AcceleratorMatchPhase match_phase);
 
   bool IsTrackingPointer(int32_t pointer_id) const {
     return pointer_targets_.count(pointer_id) > 0;