platform-window: Add a PlatformWindowFactory for creating windows.

ui/platform_window/win/win_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_WIN_WIN_WINDOW_FACTORY_H_
+#define UI_PLATFORM_WINDOW_WIN_WIN_WINDOW_FACTORY_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/platform_window/platform_window_factory.h"
+#include "ui/platform_window/win/win_window_export.h"
+
+namespace ui {
+
+class WIN_WINDOW_EXPORT WinWindowFactory : public PlatformWindowFactory {

[Ben Goodger (Google), 2014/07/23 16:03:43]

Why do we need platform versions of this? Can't we just have a
PlatformWindow::Create() that is defined on each platform? Seems like you could
still have a default factory that calls this and then a test factory that
creates something else.

[sadrul, 2014/07/23 16:40:17]

The problem here is that for ozone, there can't be an implementation of
PlatformWindow::Create() in here (since PlatformWindow is created by an
OzonePlatform implementation in the ozone target, which has an implicit
dependency on platform_window, and so there will be cyclic dependency).

+ public:
+  static PlatformWindowFactory* CreateIfNecessary();
+
+ private:
+  WinWindowFactory();
+  virtual ~WinWindowFactory();
+
+  // PlatformWindowFactory:
+  virtual scoped_ptr<PlatformWindow> CreatePlatformWindow(
+      PlatformWindowDelegate* delegate,
+      const gfx::Rect& bounds) OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(WinWindowFactory);
+};
+
+}  // namespace ui
+
+#endif  // UI_PLATFORM_WINDOW_WIN_WIN_WINDOW_FACTORY_H_