Add CommandBroker::OnTransaction to handle incoming transactions

chromeos/binder/command_stream_unittest.cc

Index: chromeos/binder/command_stream_unittest.cc
diff --git a/chromeos/binder/command_stream_unittest.cc b/chromeos/binder/command_stream_unittest.cc
index d0a4a5f61f351b2e8e081d876efb006618818ec4..16c30831889f44cd34d6166005a495d3d4d271bd 100644
--- a/chromeos/binder/command_stream_unittest.cc
+++ b/chromeos/binder/command_stream_unittest.cc
@@ -25,6 +25,8 @@ class BinderCommandStreamTest : public ::testing::Test,
   void SetUp() override { ASSERT_TRUE(driver_.Initialize()); }
 
   // CommandStream::IncomingCommandHandler override:
+  bool OnTransaction(const TransactionData& data) override { return false; }
+
   void OnReply(scoped_ptr<TransactionData> data) override {
     received_response_ = RESPONSE_REPLY;
     ASSERT_TRUE(data);