Enable subpixel positioning for internal display with dsf larger than 1.0

ui/gfx/font_render_params.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_GFX_FONT_RENDER_PARAMS_H_
 #define UI_GFX_FONT_RENDER_PARAMS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 80 matching lines @@
     const FontRenderParamsQuery& query,
     std::string* family_out);
 
 // Clears GetFontRenderParams()'s cache. Intended to be called by tests that are
 // changing Fontconfig's configuration.
 // TODO(derat): This is only defined for Linux, but OS_LINUX doesn't seem to be
 // set when font_render_params_linux_unittest.cc includes this header. Figure
 // out what's going on here.
 GFX_EXPORT void ClearFontRenderParamsCacheForTest();
 
+#if defined(OS_CHROMEOS)
+// Sets the device scale factor for FontRenderParams to decide
+// if it should enable subpixel positioning.
+GFX_EXPORT void SetFontRenderParamsDeviceScaleFactor(
+    float device_scale_factor);
+#endif
+
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_RENDER_PARAMS_H_