Introduce WindowStateDelegate::ToggleFullscreen

ash/shell/shell_delegate_impl.cc

Index: ash/shell/shell_delegate_impl.cc
diff --git a/ash/shell/shell_delegate_impl.cc b/ash/shell/shell_delegate_impl.cc
index 717d07d42ad265cc452335eaf646591e7968b137..e1ca9031b4d09d2ea06d0b379433dc72ecea8809 100644
--- a/ash/shell/shell_delegate_impl.cc
+++ b/ash/shell/shell_delegate_impl.cc
@@ -89,13 +89,6 @@ void ShellDelegateImpl::Exit() {
   base::MessageLoopForUI::current()->Quit();
 }
 
-void ShellDelegateImpl::ToggleFullscreen() {
-  // TODO(oshima): Remove this when crbug.com/309837 is implemented.
-  wm::WindowState* window_state = wm::GetActiveWindowState();
-  if (window_state)
-    window_state->ToggleMaximized();
-}
-
 keyboard::KeyboardControllerProxy*
     ShellDelegateImpl::CreateKeyboardControllerProxy() {
   return new KeyboardControllerProxyStub();