Adds ability for accelerators to add key/value pairs to KeyEvent

ui/aura/mus/window_manager_delegate.h

Index: ui/aura/mus/window_manager_delegate.h
diff --git a/ui/aura/mus/window_manager_delegate.h b/ui/aura/mus/window_manager_delegate.h
index 447a7a028ad2be017c7ba30d2e283d789fb62173..177eb7b2efe045d4e1647d34316f8ecfcb1a8b9b 100644
--- a/ui/aura/mus/window_manager_delegate.h
+++ b/ui/aura/mus/window_manager_delegate.h
@@ -10,6 +10,7 @@
 #include <map>
 #include <memory>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include "base/callback_forward.h"
@@ -132,8 +133,16 @@ class AURA_EXPORT WindowManagerDelegate {
   // Called when a display is modified.
   virtual void OnWmDisplayModified(const display::Display& display) = 0;
 
-  virtual ui::mojom::EventResult OnAccelerator(uint32_t id,
-                                               const ui::Event& event);
+  // Called when an accelerator is received. |id| is the id previously
+  // registered via AddAccelerators(). For pre-target accelerators the delegate
+  // may add key/value pairs to |properties| that are then added to the
+  // KeyEvent that is sent to the client with the focused window (only if this
+  // returns UNHANDLED). |properties| may be used to pass around state from the
+  // window manager to clients.
+  virtual ui::mojom::EventResult OnAccelerator(
+      uint32_t id,
+      const ui::Event& event,
+      std::unordered_map<std::string, std::vector<uint8_t>>* properties);
 
   virtual void OnWmPerformMoveLoop(
       Window* window,