Add context to gfx::Screen calls in support of simultaneous desktop+ash

chrome/browser/ui/host_desktop.h

 // Copyright (c) 2012 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 CHROME_BROWSER_UI_HOST_DESKTOP_H_
 #define CHROME_BROWSER_UI_HOST_DESKTOP_H_
 
+#include "ui/gfx/native_widget_types.h"
+
+class Browser;
+
 namespace chrome {
 
 // A value that specifies what desktop environment hosts a particular piece of
 // UI.
 // Note that HOST_DESKTOP_TYPE_ASH is always used on ChromeOS.
 enum HostDesktopType {
+  HOST_DESKTOP_TYPE_FIRST = 0,
+
   // The UI is hosted on the system native desktop.
-  HOST_DESKTOP_TYPE_NATIVE = 0,
+  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
 
   HOST_DESKTOP_TYPE_COUNT
 };
 
+class ScopedForceDesktopType {
+ public:
+  explicit ScopedForceDesktopType(HostDesktopType type);
+  ~ScopedForceDesktopType();
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ScopedForceDesktopType);
+  HostDesktopType previous_type_;
+  bool previous_force_;
+};
+
+HostDesktopType GetHostDesktopTypeForNativeView(gfx::NativeView native_view);
+HostDesktopType GetHostDesktopTypeForNativeWindow(
+    gfx::NativeWindow native_window);
+HostDesktopType GetHostDesktopTypeForBrowser(const Browser* browser);
+
 /*
 TODO(beng): implement utilities as needed, e.g.:
 HostDesktopType GetActiveDesktop();
-HostDesktopType GetHostDesktopTypeForNativeView(gfx::NativeView native_view);
-HostDesktopType GetHostDesktopTypeForNativeWindow(
-    gfx::NativeWindow native_window);
-HostDesktopType GetHostDesktopTypeForBrowser(Browser* browser);
 */
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_HOST_DESKTOP_H_