Not for review: Support sync init with missing or corrupt store

chrome/browser/sync/glue/sync_backend_registrar.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_GLUE_SYNC_BACKEND_REGISTRAR_H_
 #define CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_REGISTRAR_H_
 #pragma once
 
 #include <map>
 #include <vector>
@@ skipping 16 matching lines @@
 namespace browser_sync {
 
 class ChangeProcessor;
 class UIModelWorker;
 
 // A class that keep track of the workers, change processors, and
 // routing info for the enabled sync types, and also routes change
 // events to the right processors.
 class SyncBackendRegistrar : public sync_api::SyncManager::ChangeDelegate {
  public:
-  // |initial_types| contains the initial set of types to sync
-  // (initially put in the passive group).  |name| is used for
-  // debugging.  Does not take ownership of |profile| or |sync_loop|.
-  // Must be created on the UI thread.
-  SyncBackendRegistrar(syncable::ModelTypeSet initial_types,
-                       const std::string& name,
+  // |name| is used for debugging.  Does not take ownership of |profile| or
+  // |sync_loop|.  Must be created on the UI thread.
+  SyncBackendRegistrar(const std::string& name,
                        Profile* profile,
                        MessageLoop* sync_loop);
 
   // SyncBackendRegistrar must be destroyed as follows:
   //
   //   1) On the sync thread, call OnSyncerShutdownComplete() after
   //      the syncer is shutdown.
   //   2) Meanwhile, on the UI thread, call StopOnUIThread(), which
   //      blocks until OnSyncerShutdownComplete() is called.
   //   3) Destroy the SyncBackendRegistrar.
   //
   // This is to handle the complicated shutdown requirements of the
   // UIModelWorker (since the UI thread is both the main thread and a
   // thread which the syncer pushes changes to).
   virtual ~SyncBackendRegistrar();
 
+  // Informs the SyncBackendRegistrar of the currently enabled set of types.
+  // These types will be placed in the passive group.  This function should be
+  // called exactly once during startup.
+  void SetInitialTypes(syncable::ModelTypeSet initial_types);

[rlarocque, 2012/06/04 20:07:09]

I'm not a fan of this two-stage init.  It may be possible to split this class in
two in order to avoid this, but I haven't tried.  

On the plus side, this is much simpler and safer than the other schemes I tried.
 There's no need for extra inter-thread communication with this approach.  That
does a lot to reduce the amount of new code and error-handling required.  

+
   // Returns whether or not we are currently syncing encryption keys.
   // Must be called on the UI thread.
   bool IsNigoriEnabled() const;
 
   // Removes all types in |types_to_remove| from the routing info and
   // adds all the types in |types_to_add| to the routing info that are
   // not already there (initially put in the passive group).
   // |types_to_remove| and |types_to_add| must be disjoint.  Returns
   // the set of newly-added types.  Must be called on the UI thread.
   syncable::ModelTypeSet ConfigureDataTypes(
@@ skipping 81 matching lines @@
 
   // The change processors that handle the different data types.
   std::map<syncable::ModelType, ChangeProcessor*> processors_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendRegistrar);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_REGISTRAR_H_