Start to decouple display::Display from ws::PlatformDisplay.

services/ui/ws/platform_display_factory.h

 // Copyright 2015 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.
 
 #ifndef SERVICES_UI_WS_PLATFORM_DISPLAY_FACTORY_H_
 #define SERVICES_UI_WS_PLATFORM_DISPLAY_FACTORY_H_
 
 #include <memory>
 
+namespace display {
+struct ViewportMetrics;
+}
+
 namespace ui {
 namespace ws {
 
 class PlatformDisplay;
-struct PlatformDisplayInitParams;
+class ServerWindow;
 
 // Abstract factory for PlatformDisplays. Used by tests to construct test
 // PlatformDisplays.
 class PlatformDisplayFactory {
  public:
   virtual std::unique_ptr<PlatformDisplay> CreatePlatformDisplay(
-      const PlatformDisplayInitParams& init_params) = 0;
+      ServerWindow* root_window,
+      const display::ViewportMetrics& metrics) = 0;
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_PLATFORM_DISPLAY_FACTORY_H_