Add ability to change default pref values, and use in BrowserInstantController.

base/prefs/pref_registry.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 "base/prefs/pref_registry.h"
 
 #include "base/logging.h"
 #include "base/prefs/default_pref_store.h"
 #include "base/prefs/pref_store.h"
 #include "base/values.h"
@@ skipping 10 matching lines @@
 }
 
 PrefRegistry::const_iterator PrefRegistry::begin() const {
   return defaults_->begin();
 }
 
 PrefRegistry::const_iterator PrefRegistry::end() const {
   return defaults_->end();
 }
 
+void PrefRegistry::SetDefaultPrefValue(const char* pref_name,
+                                       base::Value* value) {
+  DCHECK(value);
+  if (DCHECK_IS_ON()) {
+    const base::Value* current_value = NULL;
+    DCHECK(defaults_->GetValue(pref_name, &current_value))
+        << "Setting default for unregistered pref: " << pref_name;
+    DCHECK(value->IsType(current_value->GetType()))
+        << "Wrong type for new default: " << pref_name;
+  }
+
+  defaults_->RemoveDefaultValue(pref_name);
+  defaults_->SetDefaultValue(pref_name, value);
+}
+
 void PrefRegistry::SetRegistrationCallback(
     const RegistrationCallback& callback) {
   registration_callback_ = callback;
 }
 
 void PrefRegistry::RegisterPreference(const char* path,
                                       base::Value* default_value) {
   base::Value::Type orig_type = default_value->GetType();
   DCHECK(orig_type != base::Value::TYPE_NULL &&
          orig_type != base::Value::TYPE_BINARY) <<
          "invalid preference type: " << orig_type;
   DCHECK(!defaults_->GetValue(path, NULL)) <<
       "Trying to register a previously registered pref: " << path;
 
   defaults_->SetDefaultValue(path, default_value);
 
   if (!registration_callback_.is_null())
     registration_callback_.Run(path, default_value);
 }