platform-window: Add a PlatformWindowFactory for creating windows.

ui/platform_window/platform_window_factory.h

+// 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.
+
+#ifndef UI_PLATFORM_WINDOW_PLATFORM_WINDOW_FACTORY_H_
+#define UI_PLATFORM_WINDOW_PLATFORM_WINDOW_FACTORY_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "ui/platform_window/platform_window_export.h"
+
+namespace gfx {
+class Rect;
+}
+
+namespace ui {
+
+class PlatformWindow;
+class PlatformWindowDelegate;
+
+class PLATFORM_WINDOW_EXPORT PlatformWindowFactory {
+ public:
+  PlatformWindowFactory();
+  virtual ~PlatformWindowFactory();
+
+  // Returns the singleton instance of the PlatformWindowFactory. If a factory
+  // hadn't already been created, this would create a default factory and return
+  // that. The caller does not own the factory, and should not destroy it.
+  static PlatformWindowFactory* GetInstance();
+
+  virtual scoped_ptr<PlatformWindow> CreatePlatformWindow(
+      PlatformWindowDelegate* delegate,
+      const gfx::Rect& bounds) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_PLATFORM_WINDOW_PLATFORM_WINDOW_FACTORY_H_