diff --git chrome/browser/font_family_cache.h chrome/browser/font_family_cache.h
index 459a25956e6e3..ef9148bf69e9b 100644
--- chrome/browser/font_family_cache.h
+++ chrome/browser/font_family_cache.h
@@ -19,6 +19,8 @@ class Profile;
 
 FORWARD_DECLARE_TEST(FontFamilyCacheTest, Caching);
 
+extern const char kFontFamilyCacheKey[];
+
 // Caches font family preferences associated with a PrefService. This class
 // relies on the assumption that each concatenation of map_name + '.' + script
 // is a unique string. It also relies on the assumption that the (const char*)