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

ash/wm/drag_window_resizer_unittest.cc

 // Copyright (c) 2012 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/drag_window_resizer.h"
 
 #include "ash/display/mouse_cursor_event_filter.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
@@ skipping 22 matching lines @@
 
 class DragWindowResizerTest : public test::AshTestBase {
  public:
   DragWindowResizerTest() {}
   virtual ~DragWindowResizerTest() {}
 
   virtual void SetUp() OVERRIDE {
     AshTestBase::SetUp();
     UpdateDisplay(base::StringPrintf("800x%d", kRootHeight));
 
-    aura::RootWindow* root = Shell::GetPrimaryRootWindow();
+    aura::Window* root = Shell::GetPrimaryRootWindow();
     gfx::Rect root_bounds(root->bounds());
     EXPECT_EQ(kRootHeight, root_bounds.height());
     EXPECT_EQ(800, root_bounds.width());
     Shell::GetInstance()->SetDisplayWorkAreaInsets(root, gfx::Insets());
     window_.reset(new aura::Window(&delegate_));
     window_->SetType(aura::client::WINDOW_TYPE_NORMAL);
     window_->Init(ui::LAYER_NOT_DRAWN);
     ParentWindowInPrimaryRootWindow(window_.get());
     window_->set_id(1);
 
@@ skipping 507 matching lines @@
     ASSERT_TRUE(resizer.get());
     resizer->Drag(CalculateDragPoint(*resizer, 399, 200), 0);
     EXPECT_TRUE(WarpMouseCursorIfNecessary(root_windows[0],
                                            gfx::Point(399, 200)));
     resizer->CompleteDrag(0);
   }
 }
 
 }  // namespace internal
 }  // namespace ash