Makes ui::GetSupportedScaleFactors available on platforms other than Mac

ui/base/layout.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 UI_BASE_LAYOUT_H_
 #define UI_BASE_LAYOUT_H_
 
 #include <vector>
 
 #include "build/build_config.h"
@@ skipping 35 matching lines @@
 UI_EXPORT float GetScaleFactorScale(ScaleFactor scale_factor);
 
 // Returns the ScaleFactor which most closely matches |scale|.
 // Converting from float to ScaleFactor is inefficient and should be done as
 // little as possible.
 UI_EXPORT ScaleFactor GetScaleFactorFromScale(float scale);
 
 // Returns the ScaleFactor used by |view|.
 UI_EXPORT ScaleFactor GetScaleFactorForNativeView(gfx::NativeView view);
 
-#if defined(OS_MACOSX)
-
 // Returns a vector with the scale factors which are supported by this
 // platform.
-// Only required on Mac so far.
 UI_EXPORT std::vector<ScaleFactor> GetSupportedScaleFactors();
 
+// Returns true if |scale_factor| is supported by this platform.
+UI_EXPORT bool IsScaleFactorSupported(ScaleFactor scale_factor);
+
 namespace test {
 
 UI_EXPORT void SetSupportedScaleFactors(
     const std::vector<ScaleFactor>& scale_factors);
 
 }  // namespace test
 
-#endif
-
 }  // namespace ui
 
 #endif  // UI_BASE_LAYOUT_H_