sync: don't allow NULL profile in ProfileSyncService and friends

chrome/browser/sync/sync_prefs.h

 // 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.
 
 #ifndef CHROME_BROWSER_SYNC_SYNC_PREFS_H_
 #define CHROME_BROWSER_SYNC_SYNC_PREFS_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 32 matching lines @@
 //
 //   profile_sync_service_startup_unittest.cc
 //   profile_sync_service.cc
 //   sync_setup_flow.cc
 //   sync_setup_wizard.cc
 //   sync_setup_wizard_unittest.cc
 //   two_client_preferences_sync_test.cc
 class SyncPrefs : NON_EXPORTED_BASE(public base::NonThreadSafe),
                   public base::SupportsWeakPtr<SyncPrefs> {
  public:
-  // |pref_service| may be NULL (for unit tests), but in that case no
-  // setter methods should be called.  Does not take ownership of
-  // |pref_service|.
+  // |pref_service| may not be NULL.
+  // Does not take ownership of |pref_service|.
   explicit SyncPrefs(PrefService* pref_service);
 
   virtual ~SyncPrefs();
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
   void AddSyncPrefObserver(SyncPrefObserver* sync_pref_observer);
   void RemoveSyncPrefObserver(SyncPrefObserver* sync_pref_observer);
 
   // Clears important sync preferences.
@@ skipping 103 matching lines @@
   // etc.
   typedef std::map<syncer::ModelType, syncer::ModelTypeSet> PrefGroupsMap;
   PrefGroupsMap pref_groups_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncPrefs);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_SYNC_PREFS_H_