Add a cache for FillFontFamilyMap.

base/prefs/pref_service.h

Index: base/prefs/pref_service.h
diff --git a/base/prefs/pref_service.h b/base/prefs/pref_service.h
index 186433c1b62907c16eb3360ca8d567ca2b1a07a6..0ba605e60de97955e86487b5cc4478c2bc194b18 100644
--- a/base/prefs/pref_service.h
+++ b/base/prefs/pref_service.h
@@ -17,6 +17,7 @@
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
+#include "base/containers/scoped_ptr_hash_map.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
@@ -41,6 +42,10 @@ class PrefMemberBase;
 class ScopedUserPrefUpdateBase;
 }
 
+// Base class for caches associated with the PrefService.
+class BASE_PREFS_EXPORT PrefServiceCache {
+};
+
 // Base class for PrefServices. You can use the base class to read and
 // interact with preferences, but not to register new preferences; for
 // that see e.g. PrefRegistrySimple.
@@ -270,6 +275,10 @@ class BASE_PREFS_EXPORT PrefService : public base::NonThreadSafe {
   // implemented in chrome/browser/prefs/browser_prefs.cc.
   PrefRegistry* DeprecatedGetPrefRegistry();
 
+  base::ScopedPtrHashMap<const char*, PrefServiceCache>* GetPrefsCaches() {
+    return &prefs_caches_;
+  }
+
  protected:
   // The PrefNotifier handles registering and notifying preference observers.
   // It is created and owned by this PrefService. Subclasses may access it for
@@ -353,6 +362,9 @@ class BASE_PREFS_EXPORT PrefService : public base::NonThreadSafe {
   // of registered preferences are.
   mutable PreferenceMap prefs_map_;
 
+  // General purpose caches.
+  base::ScopedPtrHashMap<const char*, PrefServiceCache> prefs_caches_;
+
   DISALLOW_COPY_AND_ASSIGN(PrefService);
 };