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

ash/display/screen_position_controller.cc

Index: ash/display/screen_position_controller.cc
diff --git a/ash/display/screen_position_controller.cc b/ash/display/screen_position_controller.cc
index c8b8c1d7562e6172aaafada3f77134175277ae1a..7f61d1aeb0aeaebd85926adfea222cd25df8e70c 100644
--- a/ash/display/screen_position_controller.cc
+++ b/ash/display/screen_position_controller.cc
@@ -92,16 +92,16 @@ std::pair<aura::RootWindow*, gfx::Point> GetRootWindowRelativeToWindow(
     root_window->GetDispatcher()->ConvertPointToNativeScreen(
         &location_in_native);
 
-    Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+    aura::Window::Windows root_windows = Shell::GetAllRootWindows();
     for (size_t i = 0; i < root_windows.size(); ++i) {
+      aura::WindowEventDispatcher* dispatcher =
+          root_windows[i]->GetDispatcher();
       const gfx::Rect native_bounds(
-          root_windows[i]->GetHostOrigin(),
-          root_windows[i]->GetHostSize());  // in px.
+          dispatcher->GetHostOrigin(),
+          dispatcher->GetHostSize());  // in px.
       if (native_bounds.Contains(location_in_native)) {
-        root_window = root_windows[i];
         location_in_root = location_in_native;
-        root_window->GetDispatcher()->ConvertPointFromNativeScreen(
-            &location_in_root);
+        dispatcher->ConvertPointFromNativeScreen(&location_in_root);
         break;
       }
     }