sync: Make nudge + config jobs reliable in SyncerThread2

chrome/browser/sync/glue/sync_backend_host.cc

Index: chrome/browser/sync/glue/sync_backend_host.cc
diff --git a/chrome/browser/sync/glue/sync_backend_host.cc b/chrome/browser/sync/glue/sync_backend_host.cc
index c317158a3de95204a4974c63e5a2d31b3d02ca50..50fc35cf4dcfb94846fd6fa0492bdf8648bc30ca 100644
--- a/chrome/browser/sync/glue/sync_backend_host.cc
+++ b/chrome/browser/sync/glue/sync_backend_host.cc
@@ -412,8 +412,10 @@ void SyncBackendHost::ConfigureDataTypes(
   // If we're doing the first configure (at startup) this is redundant as the
   // syncer thread always must start in config mode.
   if (using_new_syncer_thread_) {
-    core_->syncapi()->StartConfigurationMode(NewCallback(core_.get(),
-        &SyncBackendHost::Core::FinishConfigureDataTypes));
+    core_thread_.message_loop()->PostTask(
+        FROM_HERE,
+        NewRunnableMethod(core_.get(),
+        &SyncBackendHost::Core::DoStartConfigurationMode));
   } else {
     FinishConfigureDataTypesOnFrontendLoop();
   }
@@ -1211,6 +1213,11 @@ void SyncBackendHost::Core::DoProcessMessage(
   syncapi_->GetJsBackend()->ProcessMessage(name, args, sender);
 }
 
+void SyncBackendHost::Core::DoStartConfigurationMode() {
+  syncapi_->StartConfigurationMode(NewCallback(this,
+        &SyncBackendHost::Core::FinishConfigureDataTypes));
+}
+
 void SyncBackendHost::Core::DeferNudgeForCleanup() {
   DCHECK_EQ(MessageLoop::current(), host_->core_thread_.message_loop());
   deferred_nudge_for_cleanup_requested_ = true;