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

ui/views/widget/desktop_aura/desktop_root_window_host_win.cc

Index: ui/views/widget/desktop_aura/desktop_root_window_host_win.cc
diff --git a/ui/views/widget/desktop_aura/desktop_root_window_host_win.cc b/ui/views/widget/desktop_aura/desktop_root_window_host_win.cc
index d0c7ee240304f7ad39c9766a45eb15b97e762315..4fc9a84ee27acf3c7728e80c2c4462eee8dbd381 100644
--- a/ui/views/widget/desktop_aura/desktop_root_window_host_win.cc
+++ b/ui/views/widget/desktop_aura/desktop_root_window_host_win.cc
@@ -79,11 +79,12 @@ aura::Window* DesktopRootWindowHostWin::GetContentWindowForHWND(HWND hwnd) {
 ui::NativeTheme* DesktopRootWindowHost::GetNativeTheme(aura::Window* window) {
   // Use NativeThemeWin for windows shown on the desktop, those not on the
   // desktop come from Ash and get NativeThemeAura.
-  aura::RootWindow* root = window ? window->GetRootWindow() : NULL;
-  if (root) {
-    HWND root_hwnd = root->GetAcceleratedWidget();
-    if (root_hwnd &&
-        DesktopRootWindowHostWin::GetContentWindowForHWND(root_hwnd)) {
+  aura::WindowEventDispatcher* dispatcher =
+      window ? window->GetDispatcher() : NULL;
+  if (dispatcher) {
+    HWND host_hwnd = dispatcher->GetAcceleratedWidget();
+    if (host_hwnd &&
+        DesktopRootWindowHostWin::GetContentWindowForHWND(host_hwnd)) {
       return ui::NativeThemeWin::instance();
     }
   }
@@ -107,8 +108,8 @@ void DesktopRootWindowHostWin::Init(
                         native_widget_delegate_);
 
   HWND parent_hwnd = NULL;
-  if (params.parent && params.parent->GetRootWindow())
-    parent_hwnd = params.parent->GetRootWindow()->GetAcceleratedWidget();
+  if (params.parent && params.parent->GetDispatcher())
+    parent_hwnd = params.parent->GetDispatcher()->GetAcceleratedWidget();
 
   message_handler_->set_remove_standard_frame(params.remove_standard_frame);