Worker changes to prepare for lock-free shutdown.

chrome/browser/sync/glue/browser_thread_model_worker.cc

Index: chrome/browser/sync/glue/browser_thread_model_worker.cc
diff --git a/chrome/browser/sync/glue/browser_thread_model_worker.cc b/chrome/browser/sync/glue/browser_thread_model_worker.cc
index f92b6885f7e905cf6aef42f359bbfbea901c1b54..3d8cfa1d8aa55e40079ed33f5e99ec190635e482 100644
--- a/chrome/browser/sync/glue/browser_thread_model_worker.cc
+++ b/chrome/browser/sync/glue/browser_thread_model_worker.cc
@@ -14,28 +14,31 @@ using content::BrowserThread;
 namespace browser_sync {
 
 BrowserThreadModelWorker::BrowserThreadModelWorker(
-    BrowserThread::ID thread, syncer::ModelSafeGroup group)
-    : thread_(thread), group_(group) {
+    BrowserThread::ID thread, syncer::ModelSafeGroup group,
+    syncer::WorkerLoopDestructionObserver* observer)
+    : ModelSafeWorker(observer),
+      thread_(thread), group_(group) {
 }
 
-syncer::SyncerError BrowserThreadModelWorker::DoWorkAndWaitUntilDone(
+syncer::SyncerError BrowserThreadModelWorker::DoWorkAndWaitUntilDoneImpl(
     const syncer::WorkCallback& work) {
   syncer::SyncerError error = syncer::UNSET;
   if (BrowserThread::CurrentlyOn(thread_)) {
     DLOG(WARNING) << "Already on thread " << thread_;
     return work.Run();
   }
-  WaitableEvent done(false, false);
+
   if (!BrowserThread::PostTask(
       thread_,
       FROM_HERE,
-      base::Bind(&BrowserThreadModelWorker::CallDoWorkAndSignalTask, this,
-                 work, &done, &error))) {
+      base::Bind(&BrowserThreadModelWorker::CallDoWorkAndSignalTask,
+                 this, work,
+                 work_done_or_stopped(), &error))) {
     DLOG(WARNING) << "Failed to post task to thread " << thread_;
     error = syncer::CANNOT_DO_WORK;
     return error;
   }
-  done.Wait();
+  work_done_or_stopped()->Wait();
   return error;
 }
 
@@ -45,17 +48,29 @@ syncer::ModelSafeGroup BrowserThreadModelWorker::GetModelSafeGroup() {
 
 BrowserThreadModelWorker::~BrowserThreadModelWorker() {}
 
+void BrowserThreadModelWorker::RegisterForLoopDestruction() {
+  if (BrowserThread::CurrentlyOn(thread_)) {
+    MessageLoop::current()->AddDestructionObserver(this);
+  } else {
+    BrowserThread::PostTask(
+        thread_, FROM_HERE,
+        Bind(&BrowserThreadModelWorker::RegisterForLoopDestruction, this));
+  }
+}
+
 void BrowserThreadModelWorker::CallDoWorkAndSignalTask(
     const syncer::WorkCallback& work,
     WaitableEvent* done,
     syncer::SyncerError* error) {
   DCHECK(BrowserThread::CurrentlyOn(thread_));
-  *error = work.Run();
+  if (!IsStopped())
+    *error = work.Run();
   done->Signal();
 }
 
-DatabaseModelWorker::DatabaseModelWorker()
-    : BrowserThreadModelWorker(BrowserThread::DB, syncer::GROUP_DB) {
+DatabaseModelWorker::DatabaseModelWorker(
+    syncer::WorkerLoopDestructionObserver* observer)
+    : BrowserThreadModelWorker(BrowserThread::DB, syncer::GROUP_DB, observer) {
 }
 
 void DatabaseModelWorker::CallDoWorkAndSignalTask(
@@ -67,8 +82,10 @@ void DatabaseModelWorker::CallDoWorkAndSignalTask(
 
 DatabaseModelWorker::~DatabaseModelWorker() {}
 
-FileModelWorker::FileModelWorker()
-    : BrowserThreadModelWorker(BrowserThread::FILE, syncer::GROUP_FILE) {
+FileModelWorker::FileModelWorker(
+    syncer::WorkerLoopDestructionObserver* observer)
+    : BrowserThreadModelWorker(BrowserThread::FILE, syncer::GROUP_FILE,
+                               observer) {
 }
 
 void FileModelWorker::CallDoWorkAndSignalTask(