[Sync] Add support for immediately enabling wallet datatype

components/sync_driver/data_type_manager_impl.cc

Index: components/sync_driver/data_type_manager_impl.cc
diff --git a/components/sync_driver/data_type_manager_impl.cc b/components/sync_driver/data_type_manager_impl.cc
index dfffa3c775078403ff6a0a8aa4071e9a9dbfd68a..bc6ec16f3b56f1184d1d8582bd1b8015a65ca139 100644
--- a/components/sync_driver/data_type_manager_impl.cc
+++ b/components/sync_driver/data_type_manager_impl.cc
@@ -260,12 +260,14 @@ void DataTypeManagerImpl::Restart(syncer::ConfigureReason reason) {
 
   DCHECK(state_ == STOPPED || state_ == CONFIGURED || state_ == RETRYING);
 
+  State old_state = state_;

[maniscalco, 2015/03/25 00:31:48]

Opportunity for const,

const State old_state = state_;

[Nicolas Zea, 2015/03/25 00:41:17]

Done.

+  state_ = DOWNLOAD_PENDING;

[maniscalco, 2015/03/25 00:31:48]

So is it important that we set state_ to DOWNLOAD_PENDING *before* we call
NotifyStart() ?

[Nicolas Zea, 2015/03/25 00:41:17]

Yes, as NotifyStart() can trigger ProfileSyncServiceObservers, which might be
checking GetActiveDataTypes, which looks at the configuration state (the tests
in this patch uncovered this issue). Added a comment explaining that further.

[maniscalco, 2015/03/25 00:47:53]

Got it.  That's a helpful comment.  Thanks for adding it.

+
   // Starting from a "steady state" (stopped or configured) state
   // should send a start notification.
-  if (state_ == STOPPED || state_ == CONFIGURED)
+  if (old_state == STOPPED || old_state == CONFIGURED)
     NotifyStart();
 
-  state_ = DOWNLOAD_PENDING;
   download_types_queue_ = PrioritizeTypes(enabled_types);
   association_types_queue_ = std::queue<AssociationTypesInfo>();