login: add a test for reentrancy of ArcInstanceStopped event

In this change we're adding a test that simulates the same condition
that was addressed in https://crrev.com/c/2389060 i.e. we ensure that
ArcInstanceStopped is not called on new instances of arc_vm_client_adapter
if they're created during handling of ArcInstanceStopped event.

BUG=b:164816080
TEST=components_unittests --gtest_filter='ArcVmClientAdapterTest*'
TEST=revert the fix and ensure that the test fails

Change-Id: Icd90da53f832d13893f20bb017fdc793e14af628
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2469813Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Commit-Queue: Muhammad Hasan Khan <mhasank@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817545}

components/arc/session/arc_vm_client_adapter_unittest.cc

@@ -14,6 +14,7 @@
 #include <vector>
 
 #include "base/bind.h"
+#include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
@@ -650,6 +651,85 @@ TEST_F(ArcVmClientAdapterTest, StopArcInstance) {
   EXPECT_TRUE(arc_instance_stopped_called());
 }
 
+// b/164816080 This test ensures that a new vm instance that is
+// created while handling the shutting down of the previous instance,
+// doesn't incorrectly receive the shutdown event as well.
+TEST_F(ArcVmClientAdapterTest, DoesNotGetArcInstanceStoppedOnNestedInstance) {
+  using RunLoopFactory = base::RepeatingCallback<base::RunLoop*()>;
+
+  class Observer : public ArcClientAdapter::Observer {
+   public:
+    Observer(RunLoopFactory run_loop_factory, Observer* child_observer)
+        : run_loop_factory_(run_loop_factory),
+          child_observer_(child_observer) {}
+    Observer(const Observer&) = delete;
+    Observer& operator=(const Observer&) = delete;
+
+    ~Observer() override {
+      if (child_observer_ && nested_adapter_)
+        nested_adapter_->RemoveObserver(child_observer_);
+    }
+
+    bool stopped_called() const { return stopped_called_; }
+
+    // ArcClientAdapter::Observer:
+    void ArcInstanceStopped() override {
+      stopped_called_ = true;
+
+      if (child_observer_) {
+        nested_adapter_ = CreateArcVmClientAdapterForTesting(base::DoNothing());
+        nested_adapter_->AddObserver(child_observer_);
+        nested_adapter_->SetUserInfo(
+            cryptohome::Identification(user_manager::StubAccountId()),
+            kUserIdHash, kSerialNumber);
+
+        base::RunLoop* run_loop = run_loop_factory_.Run();
+        nested_adapter_->StartMiniArc({}, QuitClosure(run_loop));
+        run_loop->Run();
+
+        run_loop = run_loop_factory_.Run();
+        nested_adapter_->UpgradeArc({}, QuitClosure(run_loop));
+        run_loop->Run();
+      }
+    }
+
+   private:
+    base::OnceCallback<void(bool)> QuitClosure(base::RunLoop* run_loop) {
+      return base::BindOnce(
+          [](base::RunLoop* run_loop, bool result) { run_loop->Quit(); },
+          run_loop);
+    }
+
+    base::RepeatingCallback<base::RunLoop*()> const run_loop_factory_;
+    Observer* const child_observer_;
+    std::unique_ptr<ArcClientAdapter> nested_adapter_;
+    bool stopped_called_ = false;
+  };
+
+  SetValidUserInfo();
+  StartMiniArc();
+  UpgradeArc(true);
+
+  RunLoopFactory run_loop_factory = base::BindLambdaForTesting([this]() {
+    RecreateRunLoop();
+    return run_loop();
+  });
+
+  Observer child_observer(run_loop_factory, nullptr);
+  Observer parent_observer(run_loop_factory, &child_observer);
+  adapter()->AddObserver(&parent_observer);
+  base::ScopedClosureRunner teardown(base::BindOnce(
+      [](ArcClientAdapter* adapter, Observer* parent_observer) {
+        adapter->RemoveObserver(parent_observer);
+      },
+      adapter(), &parent_observer));
+
+  SendVmStoppedSignal();
+
+  EXPECT_TRUE(parent_observer.stopped_called());
+  EXPECT_FALSE(child_observer.stopped_called());
+}
+
 // Tests that StopArcInstance() initiates ARC log backup.
 TEST_F(ArcVmClientAdapterTest, StopArcInstance_WithLogBackup) {
   SetValidUserInfo();