Adds support for multiple displays to WmTestBase

ash/mus/test/wm_test_helper.h

 // 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.
 
 #ifndef ASH_MUS_TEST_WM_TEST_HELPER_H_
 #define ASH_MUS_TEST_WM_TEST_HELPER_H_
 
 #include <memory>
 
 #include "ash/mus/window_manager_application.h"
 #include "base/macros.h"
 #include "services/ui/public/cpp/tests/test_window_tree_client_setup.h"
 
 namespace base {
 class MessageLoop;
 class SequencedWorkerPoolOwner;
 }
 
 namespace gfx {
 class Rect;
 }
 
 namespace ui {
 class Window;
+class WindowTreeClientPrivate;
 }
 
 namespace ash {
 namespace mus {
 
-class WmTestScreen;
+class RootWindowController;
 
 // WMTestHelper is responsible for configuring a WindowTreeClient that
-// does not talk to mus. Additionally a test Screen (WmTestScreen) is created.
+// does not talk to mus.
 class WmTestHelper {
  public:
   WmTestHelper();
   ~WmTestHelper();
 
   void Init();
 
   WindowManagerApplication* window_manager_app() {
     return window_manager_app_.get();
   }
 
-  WmTestScreen* screen() { return screen_; }
+  // Returns the RootWindowControllers ordered by display id (which we assume
+  // correlates with creation order).
+  std::vector<RootWindowController*> GetRootsOrderedByDisplayId();
+
+  void UpdateDisplay(const std::string& display_spec);
 
  private:
+  // Creates a new RootWindowController given |display_spec|, which is the
+  // configuration of the display.
+  RootWindowController* CreateRootWindowController(
+      const std::string& display_spec);
+
+  // Updates the display of an existing RootWindowController.
+  void UpdateDisplay(RootWindowController* root_window_controller,
+                     const std::string& display_spec);
+
+  // Destroys a RootWindowController.
+  void DestroyRootWindowController(
+      RootWindowController* root_window_controller);
+
   std::unique_ptr<base::MessageLoop> message_loop_;
   ui::TestWindowTreeClientSetup window_tree_client_setup_;
   std::unique_ptr<WindowManagerApplication> window_manager_app_;
-  WmTestScreen* screen_ = nullptr;  // Owned by |window_manager_app_|.
+  std::unique_ptr<ui::WindowTreeClientPrivate> window_tree_client_private_;
+
+  // Id for the next Display created by CreateRootWindowController().
+  int64_t next_display_id_ = 1;
+
   std::unique_ptr<base::SequencedWorkerPoolOwner> blocking_pool_owner_;
 
   DISALLOW_COPY_AND_ASSIGN(WmTestHelper);
 };
 
 }  // namespace mus
 }  // namespace ash
 
 #endif  // ASH_MUS_TEST_WM_TEST_HELPER_H_