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

components/mus/public/cpp/lib/window.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/public/cpp/window.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <set>
@@ skipping 143 matching lines @@
 
 bool IsClientRoot(Window* window) {
   return window->window_tree() &&
          window->window_tree()->GetRoots().count(window) > 0;
 }
 
 bool OwnsWindowOrIsRoot(Window* window) {
   return OwnsWindow(window->window_tree(), window) || IsClientRoot(window);
 }
 
-void EmptyEmbedCallback(bool result) {}
+void EmptyEmbedCallback(bool result, mojom::InputEventHandlerPtr handler) {}
 
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // Window, public:
 
 void Window::Destroy() {
   if (!OwnsWindowOrIsRoot(this))
     return;
 
@@ skipping 275 matching lines @@
 void Window::Embed(mus::mojom::WindowTreeClientPtr client, uint32_t flags) {
   Embed(std::move(client), base::Bind(&EmptyEmbedCallback), flags);
 }
 
 void Window::Embed(mus::mojom::WindowTreeClientPtr client,
                    const EmbedCallback& callback,
                    uint32_t flags) {
   if (PrepareForEmbed())
     client_->Embed(server_id_, std::move(client), flags, callback);
   else
-    callback.Run(false);
+    callback.Run(false, nullptr);
 }
 
 void Window::RequestClose() {
   if (client_)
     client_->RequestClose(this);
 }
 
 std::string Window::GetName() const {
   if (HasSharedProperty(mojom::WindowManager::kName_Property))
     return GetSharedProperty<std::string>(mojom::WindowManager::kName_Property);
@@ skipping 411 matching lines @@
     notifier->NotifyWindowReordered();
 
   return true;
 }
 
 // static
 Window** Window::GetStackingTarget(Window* window) {
   return &window->stacking_target_;
 }
 }  // namespace mus