Adds ability for pre-target accelerators to not consume events

services/ui/public/interfaces/window_manager.mojom

Index: services/ui/public/interfaces/window_manager.mojom
diff --git a/services/ui/public/interfaces/window_manager.mojom b/services/ui/public/interfaces/window_manager.mojom
index 9b40319724451df64db5805bfb9afc2a61e787a2..aba4c24dd903566bf53699f704b7ddf4fcf77d80 100644
--- a/services/ui/public/interfaces/window_manager.mojom
+++ b/services/ui/public/interfaces/window_manager.mojom
@@ -83,8 +83,10 @@ interface WindowManager {
   // can update the UI for the janky windows.
   WmClientJankinessChanged(uint16 client_id, bool janky);
 
-  // An accelerator registered via AddAccelerator() has been triggered.
-  OnAccelerator(uint32 id, ui.mojom.Event event);
+  // An accelerator registered via AddAccelerator() has been triggered. If
+  // |ack_id| is non-zero the accelerator matches a PRE_TARGET and must be
+  // acknowledged by WindowManagerClient::OnAcceleratorAck().
+  OnAccelerator(uint32 ack_id, uint32 accelerator_id, ui.mojom.Event event);
 };
 
 // This interface is only used as an associated interface and is associated
@@ -131,4 +133,8 @@ interface WindowManagerClient {
   // Response from WmCreateTopLevelWindow() informing the client of the id for
   // the new window.
   OnWmCreatedTopLevelWindow(uint32 change_id, uint32 window_id);
+
+  // See description in WindowManager::OnAccelerator(). |ack_id| is the value
+  // that was passed to OnAccelerator().
+  OnAcceleratorAck(uint32 ack_id, EventResult event_result);
 };