Provide access to recommended pref values

chrome/browser/prefs/pref_value_store.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prefs/pref_value_store.h"
 
 #include "base/logging.h"
 #include "chrome/browser/prefs/pref_model_associator.h"
 #include "chrome/browser/prefs/pref_notifier.h"
 
@@ skipping 100 matching lines @@
                      << " but got " << (*out_value)->GetType()
                      << " in store " << i;
         continue;
       }
       return true;
     }
   }
   return false;
 }
 
+bool PrefValueStore::GetRecommendedValue(const std::string& name,
+                                         base::Value::Type type,
+                                         const Value** out_value) const {
+  *out_value = NULL;
+  if (!GetValueFromStore(name.c_str(), RECOMMENDED_STORE, out_value))
+    return false;
+  if (!(*out_value)->IsType(type)) {
+    LOG(WARNING) << "Expected type for " << name << " is " << type
+                 << " but got " << (*out_value)->GetType();
+    return false;
+   }

[Mattias Nissler (ping if slow), 2012/07/27 07:26:11]

indentation

[bartfab (slow), 2012/07/27 12:14:49]

Done.

+ return true;

[Mattias Nissler (ping if slow), 2012/07/27 07:26:11]

seems like the code in this function is essentially to loop body of GetValue()
above. Share?

[bartfab (slow), 2012/07/27 12:14:49]

Done.

+}
+
 void PrefValueStore::NotifyPrefChanged(
     const char* path,
     PrefValueStore::PrefStoreType new_store) {
   DCHECK(new_store != INVALID_STORE);
 
   // If the pref is controlled by a higher-priority store, its effective value
   // cannot have changed.
   PrefStoreType controller = ControllingPrefStoreForPref(path);
   if (controller == INVALID_STORE || controller >= new_store) {
     pref_notifier_->OnPreferenceChanged(path);
     if (pref_sync_associator_)
       pref_sync_associator_->ProcessPrefChange(path);
+  // Always fire a notification when the recommended value changes, even if the
+  // effective value is unchanged.

[Mattias Nissler (ping if slow), 2012/07/27 07:26:11]

As discussed offline, maybe we want to just drop all the filtering. Can you
instrument a build and count the number of pref change notifications sent out w/
vs. w/out the filtering? I'd like to see some number on how much impact this
has.

[bartfab (slow), 2012/07/27 12:14:49]

Fresh profile: Start browser, visit google.com, shut down: 1489 pref change
notifications, 0 of these get filtered.

Existing profile: Start browser, visit google.com, visit settings page, shut
down: 1407 pref change notifications, 72 of these get filtered.

+  } else if (new_store == RECOMMENDED_STORE) {
+    pref_notifier_->OnPreferenceChanged(path);
   }
 }
 
 bool PrefValueStore::PrefValueInManagedStore(const char* name) const {
   return PrefValueInStore(name, MANAGED_STORE);
 }
 
 bool PrefValueStore::PrefValueInExtensionStore(const char* name) const {
   return PrefValueInStore(name, EXTENSION_STORE);
 }
@@ skipping 122 matching lines @@
   if (initialization_failed_)
     return;
   for (size_t i = 0; i <= PREF_STORE_TYPE_MAX; ++i) {
     scoped_refptr<PrefStore> store =
         GetPrefStore(static_cast<PrefStoreType>(i));
     if (store && !store->IsInitializationComplete())
       return;
   }
   pref_notifier_->OnInitializationCompleted(true);
 }