Plumb explicit IPC task runner through to IPC::Channel creation

ipc/ipc_test_base.h

Index: ipc/ipc_test_base.h
diff --git a/ipc/ipc_test_base.h b/ipc/ipc_test_base.h
index c85c74f43a19e4ecb753b48cf0bc9cfe27cb5e4b..86dc8fc80551ea8a28dfc0f4b9ec1f907a881582 100644
--- a/ipc/ipc_test_base.h
+++ b/ipc/ipc_test_base.h
@@ -111,11 +111,11 @@ class IPCTestBase : public base::MultiProcessTest {
   }
 
   const base::Process& client_process() const { return client_process_; }
-  scoped_refptr<base::SequencedTaskRunner> task_runner();
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner();
 
   virtual std::unique_ptr<IPC::ChannelFactory> CreateChannelFactory(
       const IPC::ChannelHandle& handle,
-      base::SequencedTaskRunner* runner);
+      base::SingleThreadTaskRunner* runner);
 
   virtual bool DidStartClient();