Unify desktop Linux and Chrome OS font rendering params.

ui/gfx/platform_font_pango.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_GFX_PLATFORM_FONT_PANGO_H_
 #define UI_GFX_PLATFORM_FONT_PANGO_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 17 matching lines @@
   // Converts |gfx_font| to a new pango font. Free the returned font with
   // pango_font_description_free().
   static PangoFontDescription* PangoFontFromGfxFont(const gfx::Font& gfx_font);
 
   // Resets and reloads the cached system font used by the default constructor.
   // This function is useful when the system font has changed, for example, when
   // the locale has changed.
   static void ReloadDefaultFont();
 
 #if defined(OS_CHROMEOS)
-  // Sets the default font.
+  // Sets the default font. |font_description| is a Pango font description that
+  // will be passed to pango_font_description_from_string().
   static void SetDefaultFontDescription(const std::string& font_description);
 #endif
 
   // Position as an offset from the height of the drawn text, used to draw
   // an underline. This is a negative number, so the underline would be
   // drawn at y + height + underline_position.
   double underline_position() const;
   // The thickness to draw the underline.
   double underline_thickness() const;
 
@@ skipping 64 matching lines @@
   // to compute them.
   bool pango_metrics_inited_;
   double average_width_pixels_;
   double underline_position_pixels_;
   double underline_thickness_pixels_;
 
   // The default font, used for the default constructor.
   static Font* default_font_;
 
 #if defined(OS_CHROMEOS)
+  // A Pango font description.
   static std::string* default_font_description_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PlatformFontPango);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PLATFORM_FONT_PANGO_H_