Lock-free shutdown of profile sync service. Changes include:

* Disconnect non-frontend processor/associator to stop accessing directory
so that sync backend can be shut down without waiting.
* Change non-frontend controller so that creation/destruction of 
processor/associator doesn't depend on valid controller. So
scoped wait on stopping controller can be removed.
* Move sync thread to PSS. It's created when starting first backend and 
destroyed on last browser thread.

BUG=19757

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=210333

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=210955

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=213642

Review URL: https://chromiumcodereview.appspot.com/16770005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@214500 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 33 insertions, 1 deletions

diff --git a/sync/internal_api/public/engine/model_safe_worker.cc b/sync/internal_api/public/engine/model_safe_worker.cc
index 44e0a24..7179ed5 100644
--- a/sync/internal_api/public/engine/model_safe_worker.cc
+++ b/sync/internal_api/public/engine/model_safe_worker.cc
@@ -4,6 +4,7 @@
 
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 
+#include "base/bind.h"
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/values.h"
@@ -84,7 +85,9 @@ std::string ModelSafeGroupToString(ModelSafeGroup group) {
 ModelSafeWorker::ModelSafeWorker(WorkerLoopDestructionObserver* observer)
     : stopped_(false),
       work_done_or_stopped_(false, false),
-      observer_(observer) {}
+      observer_(observer),
+      working_loop_(NULL),
+      working_loop_set_wait_(true, false) {}
 
 ModelSafeWorker::~ModelSafeWorker() {}
 
@@ -135,4 +138,33 @@ void ModelSafeWorker::WillDestroyCurrentMessageLoop() {
     observer_->OnWorkerLoopDestroyed(GetModelSafeGroup());
 }
 
+void ModelSafeWorker::SetWorkingLoopToCurrent() {
+  DCHECK(!working_loop_);
+  working_loop_ = base::MessageLoop::current();
+  working_loop_set_wait_.Signal();
+}
+
+void ModelSafeWorker::UnregisterForLoopDestruction(
+    base::Callback<void(ModelSafeGroup)> unregister_done_callback) {
+  // Ok to wait until |working_loop_| is set because this is called on sync
+  // loop.
+  working_loop_set_wait_.Wait();
+
+  // Should be called on sync loop.
+  DCHECK_NE(base::MessageLoop::current(), working_loop_);
+  DCHECK(working_loop_);
+  working_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&ModelSafeWorker::UnregisterForLoopDestructionAsync,
+                 this, unregister_done_callback));
+}
+
+void ModelSafeWorker::UnregisterForLoopDestructionAsync(
+    base::Callback<void(ModelSafeGroup)> unregister_done_callback) {
+  DCHECK(stopped_);
+  DCHECK_EQ(base::MessageLoop::current(), working_loop_);
+  base::MessageLoop::current()->RemoveDestructionObserver(this);
+  unregister_done_callback.Run(GetModelSafeGroup());
+}
+
 }  // namespace syncer