Add thread checker calls to all ArcServiceManager methods

components/arc/arc_service_manager.cc

Index: components/arc/arc_service_manager.cc
diff --git a/components/arc/arc_service_manager.cc b/components/arc/arc_service_manager.cc
index 9642d9f40d16801672933118e22b7cc1851aa1b3..b9e1e8f9fdbddd02d589f73aacb13680e6e05d36 100644
--- a/components/arc/arc_service_manager.cc
+++ b/components/arc/arc_service_manager.cc
@@ -58,6 +58,8 @@ ArcServiceManager* ArcServiceManager::Get() {
 
 // static
 bool ArcServiceManager::IsInitialized() {

[Yusuke Sato, 2016/12/02 21:06:54]

FYI, this method was introduced for
https://codereview.chromium.org/2487623002/diff/480001/chrome/browser/chromeo...

I was not particularly happy with the introduction, but didn't have a better
idea. The EventRouter::Shutdown() function must call
arc::ArcServiceManager::Get()->RemoveObserver() when the event router is owned
by a non-primary Chrome profile, but it must NOT call the remove function when
the profile is primary because for primary profile destruction (i.e. shutdown)
ArcServiceManager is destructed first. If you call remove() in that case, Chrome
crashes either with DCHECK or null pointer deref.

If you have a better idea, I'll create another follow-up CL.

[Luis Héctor Chávez, 2016/12/02 22:18:08]

Not at the moment :(

+  DCHECK(!g_arc_service_manager ||

[Yusuke Sato, 2016/12/02 21:06:54]

This DCHECK does not detect wrong threading when g_arc_service_manager is null,
but I guess having this DCHECK is still better than nothing.

[Luis Héctor Chávez, 2016/12/02 22:18:08]

This is fine. We have a similar problem in ArcBridgeService:
https://cs.chromium.org/chromium/src/components/arc/arc_bridge_service.cc?q=A...

you can follow the same pattern if you want since we expect this to be called
when |g_arc_service_manager| is null.

[Yusuke Sato, 2016/12/02 22:27:28]

Thanks, done.

+         g_arc_service_manager->thread_checker_.CalledOnValidThread());
   return g_arc_service_manager;
 }
 
@@ -72,19 +74,23 @@ void ArcServiceManager::AddService(std::unique_ptr<ArcService> service) {
 }
 
 void ArcServiceManager::AddObserver(Observer* observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   observer_list_.AddObserver(observer);
 }
 
 void ArcServiceManager::RemoveObserver(Observer* observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   observer_list_.RemoveObserver(observer);
 }
 
 void ArcServiceManager::OnAppsUpdated() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   for (auto& observer : observer_list_)
     observer.OnAppsUpdated();
 }
 
 void ArcServiceManager::Shutdown() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   icon_loader_ = nullptr;
   activity_resolver_ = nullptr;
   services_.clear();