Nix GetRootWindowController, use RootWindowController::ForWindow.

ash/root_window_controller.cc

Index: ash/root_window_controller.cc
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 70ca0ef2383f31c0807b7242e69395f9ffe7e95c..3f9cda6af9a6de7501c3890cb1ae1f783bd66bc9 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -310,15 +310,16 @@ void RootWindowController::CreateForSecondaryDisplay(AshWindowTreeHost* host) {
 // static
 RootWindowController* RootWindowController::ForWindow(
     const aura::Window* window) {
-  DCHECK(window);
   CHECK(Shell::HasInstance());
-  return GetRootWindowController(window->GetRootWindow());
+  if (!window || !window->GetRootWindow())

[sky, 2017/05/31 21:12:43]

It's unfortunate we need these checks. Are you sure they are really necessary?

[msw, 2017/05/31 21:23:37]

It's ported from GetRWC, but I'll try just keeping the old DCHECK instead.

+    return nullptr;
+  return GetRootWindowSettings(window->GetRootWindow())->controller;
 }
 
 // static
 RootWindowController* RootWindowController::ForTargetRootWindow() {
   CHECK(Shell::HasInstance());
-  return GetRootWindowController(Shell::GetRootWindowForNewWindows());
+  return ForWindow(Shell::GetRootWindowForNewWindows());
 }
 
 void RootWindowController::ConfigureWidgetInitParamsForContainer(
@@ -1083,8 +1084,4 @@ void RootWindowController::OnTouchHudProjectionToggled(bool enabled) {
     DisableTouchHudProjection();
 }
 
-RootWindowController* GetRootWindowController(const aura::Window* root_window) {
-  return root_window ? GetRootWindowSettings(root_window)->controller : nullptr;
-}
-
 }  // namespace ash