mus: Introduce API for embedder to dispatch event to the embeded client.

components/mus/ws/window_tree.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/mus/ws/window_tree.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 327 matching lines @@
   Operation op(this, window_server_, OperationType::SET_FOCUS);
   bool success = window_server_->SetFocusedWindow(window);
   if (!success) {
     DVLOG(1) << "SetFocus failure, could not SetFocusedWindow.";
   }
   return success;
 }
 
 bool WindowTree::Embed(const ClientWindowId& window_id,
                        mojom::WindowTreeClientPtr client,
+                       mojom::InputEventHandlerRequest input_handler_request,
                        uint32_t flags) {
   if (!client || !CanEmbed(window_id))
     return false;
+  if (input_handler_request.is_pending())
+    client->RequestInputEventHandler(std::move(input_handler_request));
   ServerWindow* window = GetWindowByClientId(window_id);
   PrepareForEmbed(window);
   // When embedding we don't know the user id of where the TreeClient came
   // from. Use an invalid id, which limits what the client is able to do.
   window_server_->EmbedAtWindow(window, InvalidUserId(), std::move(client),
                                 flags,
                                 base::WrapUnique(new DefaultAccessPolicy));
   return true;
 }
 
@@ skipping 989 matching lines @@
   if (!mask.IsEmpty())
     window->SetHitTestMask(mask);
   else
     window->ClearHitTestMask();
 }
 
 void WindowTree::Embed(Id transport_window_id,
                        mojom::WindowTreeClientPtr client,
                        uint32_t flags,
                        const EmbedCallback& callback) {
-  callback.Run(
-      Embed(ClientWindowId(transport_window_id), std::move(client), flags));
+  bool embedder_dispatches_event_to_embeded_client =
+      !!(flags & mojom::kEmbedFlagEmbedderInterceptsEvents);
+  mojom::InputEventHandlerPtr handler;
+  mojom::InputEventHandlerRequest request =
+      embedder_dispatches_event_to_embeded_client ? GetProxy(&handler)
+                                                  : nullptr;
+  callback.Run(Embed(ClientWindowId(transport_window_id), std::move(client),
+                     std::move(request), flags),
+               std::move(handler));
 }
 
 void WindowTree::SetFocus(uint32_t change_id, Id transport_window_id) {
   client()->OnChangeCompleted(change_id,
                               SetFocus(ClientWindowId(transport_window_id)));
 }
 
 void WindowTree::SetCanFocus(Id transport_window_id, bool can_focus) {
   ServerWindow* window =
       GetWindowByClientId(ClientWindowId(transport_window_id));
@@ skipping 139 matching lines @@
 }
 
 bool WindowTree::IsWindowRootOfAnotherTreeForAccessPolicy(
     const ServerWindow* window) const {
   WindowTree* tree = window_server_->GetTreeWithRoot(window);
   return tree && tree != this;
 }
 
 }  // namespace ws
 }  // namespace mus