Eliminate Shell::RootWindowList in favor of aura::Window::Windows.

ash/high_contrast/high_contrast_controller.h

Index: ash/high_contrast/high_contrast_controller.h
diff --git a/ash/high_contrast/high_contrast_controller.h b/ash/high_contrast/high_contrast_controller.h
index 2afd60b3aa4ee1afb1f173cb5419d2819059d874..e42e46c19f4b50834240d8f36328a3bfd7df2865 100644
--- a/ash/high_contrast/high_contrast_controller.h
+++ b/ash/high_contrast/high_contrast_controller.h
@@ -10,6 +10,7 @@
 
 namespace aura {
 class RootWindow;
+class Window;
 }
 
 namespace ash {
@@ -28,7 +29,7 @@ class ASH_EXPORT HighContrastController {
 
  private:
   // Update high contrast mode on the passed display.
-  void UpdateDisplay(aura::RootWindow* root_window);
+  void UpdateDisplay(aura::Window* root_window);
 
   // Indicates if the high contrast mode is enabled or disabled.
   bool enabled_;