Add ascii() / latin1() / utf8() methods to AtomicString to avoid having to call string()

Source/platform/fonts/skia/FontCacheSkia.cpp

Index: Source/platform/fonts/skia/FontCacheSkia.cpp
diff --git a/Source/platform/fonts/skia/FontCacheSkia.cpp b/Source/platform/fonts/skia/FontCacheSkia.cpp
index 6498da1a56ec4a55e4e9fc327ff8ccacd285fd44..a0a452d0f0f915bf495025ef7d00d1f88568b2be 100644
--- a/Source/platform/fonts/skia/FontCacheSkia.cpp
+++ b/Source/platform/fonts/skia/FontCacheSkia.cpp
@@ -132,7 +132,7 @@ PassRefPtr<SkTypeface> FontCache::createTypeface(const FontDescription& fontDesc
         }
     } else {
         // convert the name to utf8
-        name = family.string().utf8();
+        name = family.utf8();
     }
 
     int style = SkTypeface::kNormal;