[tracing] Allow asynchronous unregistration of unbound dump providers

base/trace_event/memory_dump_manager_unittest.cc

Index: base/trace_event/memory_dump_manager_unittest.cc
diff --git a/base/trace_event/memory_dump_manager_unittest.cc b/base/trace_event/memory_dump_manager_unittest.cc
index 34c98b0343f0a1d41f3e025c7ce0544cf7edf72c..3b776be568bf15edd8f0b77c2ba2cf968d98d61e 100644
--- a/base/trace_event/memory_dump_manager_unittest.cc
+++ b/base/trace_event/memory_dump_manager_unittest.cc
@@ -202,10 +202,13 @@ TEST_F(MemoryDumpManagerTest, SingleDumper) {
   // Finally check the unregister logic: the delegate will be invoked but not
   // the dump provider, as it has been unregistered.
   EnableTracingWithLegacyCategories(MemoryDumpManager::kTraceCategory);
-  EXPECT_CALL(*delegate_, RequestGlobalMemoryDump(_, _)).Times(1);
+  EXPECT_CALL(*delegate_, RequestGlobalMemoryDump(_, _)).Times(3);
   EXPECT_CALL(mdp, OnMemoryDump(_, _)).Times(0);
-  RequestGlobalDumpAndWait(MemoryDumpType::EXPLICITLY_TRIGGERED,
-                           MemoryDumpLevelOfDetail::DETAILED);
+
+  for (int i = 0; i < 3; ++i) {
+    RequestGlobalDumpAndWait(MemoryDumpType::EXPLICITLY_TRIGGERED,
+                             MemoryDumpLevelOfDetail::DETAILED);
+  }
   DisableTracing();
 }
 
@@ -576,6 +579,52 @@ TEST_F(MemoryDumpManagerTest, UnregisterDumperFromThreadWhileDumping) {
   DisableTracing();
 }
 
+// If a thread (with a dump provider living on it) is torn down during a dump
+// its dump provider should be skipped but the dump itself shall succeed.
+TEST_F(MemoryDumpManagerTest, TearDownThreadWhileDumping) {
+  InitializeMemoryDumpManager(false /* is_coordinator */);
+  ScopedVector<TestIOThread> threads;

[Ruud van Asseldonk, 2015/12/14 16:25:49]

Scoped vectors are being removed in favour of |std::vector<scoped_ptr<T>>|.

+  ScopedVector<MockMemoryDumpProvider> mdps;
+
+  for (int i = 0; i < 2; i++) {
+    threads.push_back(new TestIOThread(TestIOThread::kAutoStart));
+    mdps.push_back(new MockMemoryDumpProvider());
+    RegisterDumpProvider(mdps.back(), threads.back()->task_runner(),
+                         kDefaultOptions);
+  }
+
+  int on_memory_dump_call_count = 0;
+
+  // When OnMemoryDump is called on either of the dump providers, it will
+  // tear down the thread of the other one.
+  for (MockMemoryDumpProvider* mdp : mdps) {
+    int other_idx = (mdps.front() == mdp);
+    TestIOThread* other_thread = threads[other_idx];
+    auto on_dump = [other_thread, &on_memory_dump_call_count](
+        const MemoryDumpArgs& args, ProcessMemoryDump* pmd) {
+      other_thread->Stop();
+      on_memory_dump_call_count++;
+      return true;
+    };
+
+    // OnMemoryDump is called once for the provider that dumps first, and zero
+    // times for the other provider.
+    EXPECT_CALL(*mdp, OnMemoryDump(_, _))
+        .Times(AtMost(1))
+        .WillOnce(Invoke(on_dump));
+  }
+
+  last_callback_success_ = false;
+  EnableTracingWithLegacyCategories(MemoryDumpManager::kTraceCategory);
+  EXPECT_CALL(*delegate_, RequestGlobalMemoryDump(_, _)).Times(1);
+  RequestGlobalDumpAndWait(MemoryDumpType::EXPLICITLY_TRIGGERED,
+                           MemoryDumpLevelOfDetail::DETAILED);
+  ASSERT_EQ(1, on_memory_dump_call_count);
+  ASSERT_EQ(true, last_callback_success_);
+
+  DisableTracing();
+}
+
 // Checks that a NACK callback is invoked if RequestGlobalDump() is called when
 // tracing is not enabled.
 TEST_F(MemoryDumpManagerTest, CallbackCalledOnFailure) {
@@ -761,9 +810,9 @@ TEST_F(MemoryDumpManagerTest, DisableTracingWhileDumping) {
   tracing_disabled_event.Signal();
   run_loop.Run();
 
-  // RequestGlobalMemoryDump() should be NACK-ed because one of the threads
-  // threads died before we had a chance to PostTask onto them.
-  EXPECT_FALSE(last_callback_success_);
+  // RequestGlobalMemoryDump() should still suceed even if some threads were
+  // torn down during the dump.
+  EXPECT_TRUE(last_callback_success_);
 }
 
 TEST_F(MemoryDumpManagerTest, DumpOnBehalfOfOtherProcess) {