Persist Directory to disk when the app is backgrounded.

chrome/browser/sync/glue/sync_backend_host_impl.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_impl.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 15 matching lines @@
 #include "sync/internal_api/public/base_transaction.h"
 #include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/internal_api/public/http_bridge.h"
 #include "sync/internal_api/public/internal_components_factory.h"
 #include "sync/internal_api/public/internal_components_factory_impl.h"
 #include "sync/internal_api/public/network_resources.h"
 #include "sync/internal_api/public/sync_manager.h"
 #include "sync/internal_api/public/sync_manager_factory.h"
 #include "sync/internal_api/public/util/experiments.h"
 #include "sync/internal_api/public/util/sync_string_conversions.h"
+#include "sync/syncable/directory.h"
 
 // Helper macros to log with the syncer thread name; useful when there
 // are multiple syncers involved.
 
 #define SLOG(severity) LOG(severity) << name_ << ": "
 
 #define SDVLOG(verbose_level) DVLOG(verbose_level) << name_ << ": "
 
 using syncer::InternalComponentsFactory;
 
@@ skipping 467 matching lines @@
     NOTREACHED();
   }
 }
 
 SyncedDeviceTracker* SyncBackendHostImpl::GetSyncedDeviceTracker() const {
   if (!initialized())
     return NULL;
   return core_->synced_device_tracker();
 }
 
+void FlushDirectoryWrapper(syncer::syncable::Directory* directory) {

[maniscalco, 2014/09/10 17:49:03]

What's the motivation for using this free function in the Bind instead of
binding to Directory::SaveChanges?

[maxbogue, 2014/09/10 20:11:01]

Directory::SaveChanges returns a bool, so it cannot be used as a Closure. Added
a comment saying so.

[maniscalco, 2014/09/10 20:19:25]

Ah, check out IgnoreResult:

https://code.google.com/p/chromium/codesearch#chromium/src/base/callback.h&l=167

That should let you forego the extra free function.

[maxbogue, 2014/09/12 16:45:38]

Done.

+  directory->SaveChanges();
+}
+
+void SyncBackendHostImpl::FlushDirectory() const {

[nyquist, 2014/09/10 17:43:09]

Does this require the sync engine to be initialized?

[maxbogue, 2014/09/10 20:11:01]

I kind of assumed that directory being NULL meant sync was uninitialized,
meaning this function can be called but does nothing if it's not initialized.
Nicholas, is that correct?

+  syncer::syncable::Directory* directory = GetUserShare()->directory.get();
+  if (directory != nullptr) {

[nyquist, 2014/09/10 17:43:09]

!= NULL ?

[maxbogue, 2014/09/10 20:11:01]

Done.

+    registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+        base::Bind(&FlushDirectoryWrapper, directory));

[maniscalco, 2014/09/10 20:19:25]

As we talked about in person over lunch, it seems like the tricky part is
ensuring that when the task eventually executes in the sync thread, the
directory is still around.  It seems like we could end up calling SaveChanges on
a deleted Directory.  Maybe zea@ has some suggestions here?

[maxbogue, 2014/09/12 16:45:38]

Routed through SyncBackendHostCore to try to solve this problem.

+  }
+}
+
 void SyncBackendHostImpl::RequestBufferedProtocolEventsAndEnableForwarding() {
   registrar_->sync_thread()->message_loop()->PostTask(
       FROM_HERE,
       base::Bind(
           &SyncBackendHostCore::SendBufferedProtocolEventsAndEnableForwarding,
           core_));
 }
 
 void SyncBackendHostImpl::DisableProtocolEventForwarding() {
   registrar_->sync_thread()->message_loop()->PostTask(
@@ skipping 351 matching lines @@
 
 base::MessageLoop* SyncBackendHostImpl::GetSyncLoopForTesting() {
   return registrar_->sync_thread()->message_loop();
 }
 
 }  // namespace browser_sync
 
 #undef SDVLOG
 
 #undef SLOG