Move chrome::HostDesktopType to ui::HostDesktopType

ui/gfx/host_desktop_type.h

+// 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.
+
+#ifndef UI_GFX_HOST_DESKTOP_TYPE_H_
+#define UI_GFX_HOST_DESKTOP_TYPE_H_
+
+#include "build/build_config.h"
+
+namespace ui {
+
+// A value that specifies what desktop environment hosts a particular piece of
+// UI. You should almost never manually hardcode one of these enums manually,
+// please refer to the following document for details on getting the right
+// HostDesktopType:
+// http://sites.google.com/a/chromium.org/dev/developers/design-documents/aura/multi-desktop
+enum HostDesktopType {
+  HOST_DESKTOP_TYPE_FIRST = 0,
+
+  // The UI is hosted on the system native desktop.
+  HOST_DESKTOP_TYPE_NATIVE = HOST_DESKTOP_TYPE_FIRST,
+
+// The UI is hosted in the synthetic Ash desktop.
+#if defined(OS_CHROMEOS)
+  HOST_DESKTOP_TYPE_ASH = HOST_DESKTOP_TYPE_NATIVE,
+#else
+  HOST_DESKTOP_TYPE_ASH,
+#endif

[sadrul, 2015/09/11 14:03:32]

gfx shouldn't normally refer to layers above it (ash in this case). And
desktop-type is probably something we can get rid of soon
(https://groups.google.com/a/chromium.org/forum/#!msg/chromium-dev/PkYHtUn8NI8...).

[blundell, 2015/09/11 14:09:47]

I'm not very familiar with the dependency hierarchy at this level, so if there's
a more sensible location for this enum (that //components can see), I'm happy to
move it.

Re: the email thread, I'm looking to componentize tab restore code now (within
the next two weeks or so).

+
+  HOST_DESKTOP_TYPE_COUNT
+};
+
+}  // namespace ui
+
+#endif  // UI_GFX_HOST_DESKTOP_TYPE_H_