Add non-blocking sync code to ProfileSyncService

chrome/browser/sync/glue/sync_backend_host_core.cc

 // Copyright 2013 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/sync/glue/sync_backend_host_core.h"
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/metrics/histogram.h"
 #include "chrome/browser/sync/glue/device_info.h"
@@ skipping 455 matching lines @@
   // provide a callback for when it finishes.
   synced_device_tracker_.reset(
       new SyncedDeviceTracker(sync_manager_->GetUserShare(),
                               sync_manager_->cache_guid()));
   synced_device_tracker_->InitLocalDeviceInfo(
       base::Bind(&SyncBackendHostCore::DoFinishInitialProcessControlTypes,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void SyncBackendHostCore::DoFinishInitialProcessControlTypes() {
+  DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
+
   registrar_->ActivateDataType(syncer::DEVICE_INFO,
                                syncer::GROUP_PASSIVE,
                                synced_device_tracker_.get(),
                                sync_manager_->GetUserShare());
 
+  base::WeakPtr<syncer::SyncCore> sync_core = sync_manager_->GetSyncCore();
+
+  // De-reference the WeakPtr while we're here to signal to the debugging
+  // mechanisms that it belongs to the sync thread.  This helps us DCHECK
+  // earlier if the pointer is misused.
+  sync_core.get();

[Nicolas Zea, 2014/04/02 23:19:05]

I don't think this is necessary. A weak pointer always belongs to the thread it
was created on (see the constructor for SequenceCheckerImpl). It's only verified
when IsValid is checked, but the ownership is assigned at construction time.

[rlarocque, 2014/04/03 01:03:46]

IIRC, I added this statement because it helped me debug a crash, then decided to
leave it in since it was helpful.

The WeakReference::Flag constructor calls DetachFromSequence() on its
SequenceChecker.  Wouldn't that undo the association created in the
SequenceChecker's construction?

[Nicolas Zea, 2014/04/03 17:52:15]

Huh, I missed that. Fair enough then.

+
   host_.Call(
       FROM_HERE,
       &SyncBackendHostImpl::HandleInitializationSuccessOnFrontendLoop,
       js_backend_,
-      debug_info_listener_);
+      debug_info_listener_,
+      sync_core);
 
   js_backend_.Reset();
   debug_info_listener_.Reset();
 }
 
 void SyncBackendHostCore::DoSetDecryptionPassphrase(
     const std::string& passphrase) {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->GetEncryptionHandler()->SetDecryptionPassphrase(
       passphrase);
@@ skipping 134 matching lines @@
       this, &SyncBackendHostCore::SaveChanges);
 }
 
 void SyncBackendHostCore::SaveChanges() {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->SaveChanges();
 }
 
 }  // namespace browser_sync