Add more per-tab preferences.

chrome/browser/prefs/pref_model_associator.cc

Index: chrome/browser/prefs/pref_model_associator.cc
diff --git a/chrome/browser/prefs/pref_model_associator.cc b/chrome/browser/prefs/pref_model_associator.cc
index 4f06c19b34f01c6ea0c3465da48b9c897166b926..45d4332622cebdb8bf5e2c09bc3779767041daaa 100644
--- a/chrome/browser/prefs/pref_model_associator.cc
+++ b/chrome/browser/prefs/pref_model_associator.cc
@@ -376,6 +376,11 @@ bool PrefModelAssociator::IsPrefRegistered(const char* name) {
   return registered_preferences_.count(name) > 0;
 }
 
+void PrefModelAssociator::UnregisterPref(const char* name) {
+  DCHECK(synced_preferences_.count(name) == 0);
+  registered_preferences_.erase(name);
+}
+
 void PrefModelAssociator::ProcessPrefChange(const std::string& name) {
   if (processing_syncer_changes_)
     return;  // These are changes originating from us, ignore.