RenderTextHarfBuzz: Implement font fallback for Win and Linux

ui/gfx/font_fallback_win.h

Index: ui/gfx/font_fallback_win.h
diff --git a/ui/gfx/font_fallback_win.h b/ui/gfx/font_fallback_win.h
index ee675714e7f735eb86999d3ba2f3b1b2d6c0ad19..bba071d0a3c0607d96f6c59625e7a0976f8ea1c3 100644
--- a/ui/gfx/font_fallback_win.h
+++ b/ui/gfx/font_fallback_win.h
@@ -29,8 +29,6 @@ void GFX_EXPORT ParseFontLinkEntry(const std::string& entry,
 void GFX_EXPORT ParseFontFamilyString(const std::string& family,
                                      std::vector<std::string>* font_names);
 
-}  // namespace internal
-
 // Iterator over linked fallback fonts for a given font. The linked font chain
 // comes from the Windows registry, but gets cached between uses.
 class GFX_EXPORT LinkedFontsIterator {
@@ -77,6 +75,8 @@ class GFX_EXPORT LinkedFontsIterator {
   DISALLOW_COPY_AND_ASSIGN(LinkedFontsIterator);
 };
 
+}  // namespace internal
+
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_FALLBACK_WIN_H_