Make GetRootWindow() return a Window instead of a RootWindow.

ash/wm/panels/panel_window_resizer_unittest.cc

 // Copyright (c) 2013 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 "ash/wm/panels/panel_window_resizer.h"
 
 #include "ash/launcher/launcher.h"
 #include "ash/launcher/launcher_model.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_layout_manager.h"
@@ skipping 84 matching lines @@
   void DragRevert() {
     resizer_->RevertDrag();
     resizer_.reset();
   }
 
   // Test dragging the panel slightly, then detaching, and then reattaching
   // dragging out by the vector (dx, dy).
   void DetachReattachTest(aura::Window* window, int dx, int dy) {
     wm::WindowState* window_state = wm::GetWindowState(window);
     EXPECT_TRUE(window_state->panel_attached());
-    aura::RootWindow* root_window = window->GetRootWindow();
+    aura::Window* root_window = window->GetRootWindow();
     EXPECT_EQ(internal::kShellWindowId_PanelContainer, window->parent()->id());
     DragStart(window);
     gfx::Rect initial_bounds = window->GetBoundsInScreen();
 
     // Drag the panel slightly. The window should still be snapped to the
     // launcher.
     DragMove(dx * 5, dy * 5);
     EXPECT_EQ(initial_bounds.x(), window->GetBoundsInScreen().x());
     EXPECT_EQ(initial_bounds.y(), window->GetBoundsInScreen().y());
 
@@ skipping 411 matching lines @@
 
 INSTANTIATE_TEST_CASE_P(LtrRtl, PanelWindowResizerTextDirectionTest,
                         testing::Bool());
 INSTANTIATE_TEST_CASE_P(NormalPanelPopup, PanelWindowResizerTransientTest,
                         testing::Values(aura::client::WINDOW_TYPE_NORMAL,
                                         aura::client::WINDOW_TYPE_PANEL,
                                         aura::client::WINDOW_TYPE_POPUP));
 
 }  // namespace internal
 }  // namespace ash