Move GetCursor() method from WindowDelegate to its own delegate interface CursorDelegate.

ui/wm/public/cursor_delegate.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/wm/public/cursor_delegate.h"
+
+#include "ui/aura/window.h"
+#include "ui/aura/window_property.h"
+
+DECLARE_WINDOW_PROPERTY_TYPE(wm::CursorDelegate*);
+
+namespace wm {
+
+DEFINE_LOCAL_WINDOW_PROPERTY_KEY(CursorDelegate*, kCursorDelegateKey, NULL);
+
+void SetCursorDelegate(aura::Window* window, CursorDelegate* delegate) {
+  window->SetProperty(kCursorDelegateKey, delegate);
+}
+
+CursorDelegate* GetCursorDelegate(aura::Window* window) {
+  return window ? window->GetProperty(kCursorDelegateKey) : NULL;
+}
+
+}  // namespace wm