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

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 5f5ff4cdcd67425d3d866a12fb5003153b24ad81..b872edb24cfd1c9e5e37866563b9381d4e7aabbd 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -1591,10 +1591,12 @@ void WindowTreeClient::OnAccelerator(uint32_t ack_id,
                                      uint32_t accelerator_id,
                                      std::unique_ptr<ui::Event> event) {
   DCHECK(event);
-  const ui::mojom::EventResult result =
-      window_manager_delegate_->OnAccelerator(accelerator_id, *event.get());
+  std::unordered_map<std::string, std::vector<uint8_t>> properties;
+  const ui::mojom::EventResult result = window_manager_delegate_->OnAccelerator(
+      accelerator_id, *event.get(), &properties);
   if (ack_id && window_manager_internal_client_)
-    window_manager_internal_client_->OnAcceleratorAck(ack_id, result);
+    window_manager_internal_client_->OnAcceleratorAck(ack_id, result,
+                                                      properties);
 }
 
 void WindowTreeClient::SetFrameDecorationValues(