Avoid duplicate instance stopping at Service Manager shutdown

Instances are explicitly stopped during Service Manager shutdown, but
then "stopped" again during individual Instance destruction. That
results in listeners being notified twice about each instance being
stopped if they aren't stopped before Service Manager shutdown.

This CL fixes that.

Bug: 831386
Change-Id: I210c9ce07cfa386d39bba7aa42244e00519b6f81
Reviewed-on: https://chromium-review.googlesource.com/1008968Reviewed-by: Jay Civelli <jcivelli@chromium.org>
Commit-Queue: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550179}

services/service_manager/service_manager.cc

@@ -228,6 +228,8 @@ class ServiceManager::Instance
   }
 
   void Stop() {
+    DCHECK_NE(state_, State::STOPPED);
+
     // Shutdown all bindings. This way the process should see the pipes closed
     // and exit, as well as waking up any potential
     // sync/WaitForIncomingResponse().
@@ -244,10 +246,15 @@ class ServiceManager::Instance
       // Notify the ServiceManager that this Instance is really going away.
       service_manager_->OnInstanceStopped(identity_);
     }
+
+    state_ = State::STOPPED;
   }
 
   ~Instance() override {
-    Stop();
+    // The instance may have already been stopped prior to destruction if the
+    // ServiceManager itself is being torn down.
+    if (state_ != State::STOPPED)
+      Stop();
   }
 
   bool CallOnBindInterface(std::unique_ptr<ConnectParams>* in_params) {
@@ -373,7 +380,10 @@ class ServiceManager::Instance
     STARTING,
 
     // The service was started successfully.
-    STARTED
+    STARTED,
+
+    // The service has been stopped.
+    STOPPED,
   };
 
   class InterfaceProviderImpl : public mojom::InterfaceProvider {
@@ -897,10 +907,12 @@ ServiceManager::~ServiceManager() {
   // the case where one Instance's destructor blocks waiting for its Runner to
   // quit, while that Runner's corresponding Service blocks its shutdown on a
   // distinct Service receiving a connection error.
-  for (const auto& instance : instances_)
-    instance.first->Stop();
-  service_manager_instance->Stop();
+  for (const auto& instance : instances_) {
+    if (instance.first != service_manager_instance_)
+      instance.first->Stop();
+  }
 
+  service_manager_instance->Stop();
   instances_.clear();
 }