When a font family pref changes to the empty string, pass it to WebKit.

chrome/common/pref_names.h

Index: chrome/common/pref_names.h
diff --git a/chrome/common/pref_names.h b/chrome/common/pref_names.h
index cd6bb5f34164cb5cda1f1ee3706b23f07074a643..101beb842d952fa2f47a488cc6f580592b5d0b79 100644
--- a/chrome/common/pref_names.h
+++ b/chrome/common/pref_names.h
@@ -74,6 +74,13 @@ extern const char kWebKitSansSerifFontFamily[];
 extern const char kWebKitCursiveFontFamily[];
 extern const char kWebKitFantasyFontFamily[];
 extern const char kWebKitPictographFontFamily[];
+
+// ISO 15924 four-letter script codes that per-script font prefs are supported
+// for.
+extern const char* const kWebKitScriptsForFontFamilyMaps[];
+extern const size_t kWebKitScriptsForFontFamilyMapsLength;
+
+// Per-script font pref prefixes.
 extern const char kWebKitStandardFontFamilyMap[];
 extern const char kWebKitFixedFontFamilyMap[];
 extern const char kWebKitSerifFontFamilyMap[];
@@ -82,11 +89,6 @@ extern const char kWebKitCursiveFontFamilyMap[];
 extern const char kWebKitFantasyFontFamilyMap[];
 extern const char kWebKitPictographFontFamilyMap[];
 
-// ISO 15924 four-letter script codes that per-script font prefs are supported
-// for.
-extern const char* const kWebKitScriptsForFontFamilyMaps[];
-extern const size_t kWebKitScriptsForFontFamilyMapsLength;
-
 // Per-script font prefs that have defaults, for easy reference when registering
 // the defaults.
 extern const char kWebKitStandardFontFamilyArabic[];