aura: Unify WindowTreeHost for some platforms

ui/platform_window/platform_window.cc

Index: ui/platform_window/platform_window.cc
diff --git a/ui/platform_window/platform_window.cc b/ui/platform_window/platform_window.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cfedc4eae884b6580bfa6edac9e6345c3a115daf
--- /dev/null
+++ b/ui/platform_window/platform_window.cc
@@ -0,0 +1,32 @@
+// Copyright 2015 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/platform_window/platform_window.h"
+
+#if defined(OS_WIN)
+#include "ui/platform_window/win/win_window.h"
+#elif defined(USE_OZONE)
+#include "ui/ozone/public/ozone_platform.h"

[sadrul, 2015/10/08 15:18:10]

We can't depend on ozone from here, since ozone also depends on
ui/platform_window. An earlier attempt to resolve this was to introduce a
PlatformWindowFactory (https://codereview.chromium.org/403263002/). Ultimately
for mandoline/mus, we went with #ifdefs
(https://code.google.com/p/chromium/codesearch#chromium/src/components/mus/vm/...).
Maybe we can just do that in WindowTreeHost too?

[no sievers, 2015/10/09 00:34:18]

Done.

+#endif
+
+namespace ui {
+
+#if defined(OS_WIN)
+// static
+scoped_ptr<PlatformWindow> PlatformWindow::Create(
+    PlatformWindowDelegate* delegate,
+    const gfx::Rect& bounds) {
+  return new WinWindow(delegate, bounds);
+}
+#elif defined(USE_OZONE)
+// static
+scoped_ptr<PlatformWindow> PlatformWindow::Create(
+    PlatformWindowDelegate* delegate,
+    const gfx::Rect& bounds) {
+  return ui::OzonePlatform::GetInstance()->CreatePlatformWindow(delegate,
+                                                                bounds);
+}
+#endif
+
+}  // namespace ui