Adds ability for pre-target accelerators to not consume events

ash/mus/window_manager.cc

Index: ash/mus/window_manager.cc
diff --git a/ash/mus/window_manager.cc b/ash/mus/window_manager.cc
index b14cae6c75e068c3472064dbf243ed63b3bcd67e..715d740ff71f043bf4bd9dcb54c15cbc44a31dcf 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -230,18 +230,6 @@ void WindowManager::OnWmNewDisplay(::ui::Window* window,
   CreateRootWindowController(window, display);
 }
 
-void WindowManager::OnAccelerator(uint32_t id, const ui::Event& event) {
-  switch (id) {
-    case kWindowSwitchAccelerator:
-      window_manager_client()->ActivateNextWindow();
-      break;
-    default:
-      FOR_EACH_OBSERVER(WindowManagerObserver, observers_,
-                        OnAccelerator(id, event));
-      break;
-  }
-}
-
 void WindowManager::OnWmPerformMoveLoop(
     ::ui::Window* window,
     ::ui::mojom::MoveLoopSource source,
@@ -254,5 +242,19 @@ void WindowManager::OnWmCancelMoveLoop(::ui::Window* window) {
   NOTIMPLEMENTED();
 }
 
+ui::mojom::EventResult WindowManager::OnAccelerator(uint32_t id,
+                                                    const ui::Event& event) {
+  switch (id) {
+    case kWindowSwitchAccelerator:
+      window_manager_client()->ActivateNextWindow();
+      break;
+    default:
+      FOR_EACH_OBSERVER(WindowManagerObserver, observers_,
+                        OnAccelerator(id, event));
+      break;
+  }
+  return ui::mojom::EventResult::HANDLED;
+}
+
 }  // namespace mus
 }  // namespace ash