Make memory-infra tests register / unregister with thread safety

components/tracing/child/child_trace_message_filter_browsertest.cc

Index: components/tracing/child/child_trace_message_filter_browsertest.cc
diff --git a/components/tracing/child/child_trace_message_filter_browsertest.cc b/components/tracing/child/child_trace_message_filter_browsertest.cc
index 156de40fef4aa25e89bd0f3c83bee045c998604d..d0d2d020a880335cbb508a498e4a276a664052c7 100644
--- a/components/tracing/child/child_trace_message_filter_browsertest.cc
+++ b/components/tracing/child/child_trace_message_filter_browsertest.cc
@@ -55,7 +55,8 @@ class ChildTracingTest : public content::RenderViewTest, public IPC::Listener {
     // registered itself by now; this cannot be prevented easily.
     mock_dump_provider_.reset(new MockDumpProvider());
     MemoryDumpManager::GetInstance()->RegisterDumpProvider(
-        mock_dump_provider_.get(), "MockDumpProvider", nullptr);
+        mock_dump_provider_.get(), "MockDumpProvider",
+        base::ThreadTaskRunnerHandle::Get());
     MemoryDumpManager::GetInstance()
         ->set_dumper_registrations_ignored_for_testing(true);