[Sync] Add support for enabling/disabling an extension before it's installed

chrome/browser/extensions/extension_pref_value_map.cc

 // Copyright (c) 2011 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/extensions/extension_pref_value_map.h"
 
 #include "base/stl_util-inl.h"
 #include "base/values.h"
 #include "chrome/browser/prefs/pref_value_map.h"
 
@@ skipping 83 matching lines @@
 
   delete i->second;
   entries_.erase(i);
 
   NotifyPrefValueChanged(keys);
 }
 
 void ExtensionPrefValueMap::SetExtensionState(const std::string& ext_id,
                                               bool is_enabled) {
   ExtensionEntryMap::const_iterator i = entries_.find(ext_id);
-  CHECK(i != entries_.end());
+  // This may happen when sync sets the extension state for an
+  // extension that is not installed.
+  if (i == entries_.end())
+    return;
   if (i->second->enabled == is_enabled)
     return;
   std::set<std::string> keys;  // keys set by this extension
   GetExtensionControlledKeys(*(i->second), &keys);
   i->second->enabled = is_enabled;
   NotifyPrefValueChanged(keys);
 }
 
 PrefValueMap* ExtensionPrefValueMap::GetExtensionPrefValueMap(
     const std::string& ext_id,
@@ skipping 121 matching lines @@
 
 void ExtensionPrefValueMap::NotifyPrefValueChanged(const std::string& key) {
   FOR_EACH_OBSERVER(ExtensionPrefValueMap::Observer, observers_,
                     OnPrefValueChanged(key));
 }
 
 void ExtensionPrefValueMap::NotifyOfDestruction() {
   FOR_EACH_OBSERVER(ExtensionPrefValueMap::Observer, observers_,
                     OnExtensionPrefValueMapDestruction());
 }