Mojo C++ bindings: switch part of the services/ui/public/interfaces mojom target to use STL types.

services/ui/ws/window_server_test_impl.cc

 // Copyright 2016 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 "services/ui/ws/window_server_test_impl.h"
 
 #include "services/ui/public/interfaces/window_tree.mojom.h"
 #include "services/ui/ws/server_window.h"
 #include "services/ui/ws/server_window_compositor_frame_sink_manager.h"
 #include "services/ui/ws/window_server.h"
@@ skipping 26 matching lines @@
   WindowTree* tree = window_server_->GetTreeWithClientName(name);
   if (!tree)
     return;
   if (tree->HasRoot(window) && WindowHasValidFrame(window)) {
     cb.Run(true);
     window_server_->SetPaintCallback(base::Callback<void(ServerWindow*)>());
   }
 }
 
 void WindowServerTestImpl::EnsureClientHasDrawnWindow(
-    const mojo::String& client_name,
+    const std::string& client_name,
     const EnsureClientHasDrawnWindowCallback& callback) {
-  std::string name = client_name.To<std::string>();
-  WindowTree* tree = window_server_->GetTreeWithClientName(name);
+  WindowTree* tree = window_server_->GetTreeWithClientName(client_name);
   if (tree) {
     for (const ServerWindow* window : tree->roots()) {
       if (WindowHasValidFrame(window)) {
         callback.Run(true);
         return;
       }
     }
   }
 
   window_server_->SetPaintCallback(
       base::Bind(&WindowServerTestImpl::OnWindowPaint, base::Unretained(this),
-                 name, std::move(callback)));
+                 client_name, std::move(callback)));
 }
 
 }  // namespace ws
 }  // namespace ui