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

ash/wm/gestures/long_press_affordance_handler.cc

Index: ash/wm/gestures/long_press_affordance_handler.cc
diff --git a/ash/wm/gestures/long_press_affordance_handler.cc b/ash/wm/gestures/long_press_affordance_handler.cc
index 9747706304e716306da531d83772220b965a64e7..8faa78f583c19f086120c0b1da5a0b456d2225d6 100644
--- a/ash/wm/gestures/long_press_affordance_handler.cc
+++ b/ash/wm/gestures/long_press_affordance_handler.cc
@@ -59,7 +59,7 @@ const SkColor kAffordanceGlowEndColor = SkColorSetARGB(0, 255, 255, 255);
 const SkColor kAffordanceArcColor = SkColorSetARGB(80, 0, 0, 0);
 const int kAffordanceFrameRateHz = 60;
 
-views::Widget* CreateAffordanceWidget(aura::RootWindow* root_window) {
+views::Widget* CreateAffordanceWidget(aura::Window* root_window) {
   views::Widget* widget = new views::Widget;
   views::Widget::InitParams params;
   params.type = views::Widget::InitParams::TYPE_WINDOW_FRAMELESS;
@@ -140,7 +140,7 @@ class LongPressAffordanceHandler::LongPressAffordanceView
     : public views::View {
  public:
   LongPressAffordanceView(const gfx::Point& event_location,
-                          aura::RootWindow* root_window)
+                          aura::Window* root_window)
       : views::View(),
         widget_(CreateAffordanceWidget(root_window)),
         current_angle_(kAffordanceAngleStartValue),
@@ -292,7 +292,7 @@ void LongPressAffordanceHandler::ProcessEvent(aura::Window* target,
 // LongPressAffordanceHandler, private
 
 void LongPressAffordanceHandler::StartAnimation() {
-  aura::RootWindow* root_window = NULL;
+  aura::Window* root_window = NULL;
   switch (current_animation_type_) {
     case GROW_ANIMATION:
       root_window = Shell::GetInstance()->display_controller()->