Add a simple QuicTransport server for testing and demo purposes.

The server currently has two modes, echo and discard.  I've changed the integration test to use the simple server instead of a session with a mock visitor.

This CL also adds some of the missing APIs and fixes some of the bugs I've found while doing this.

gfe-relnote: n/a (code not used)
PiperOrigin-RevId: 278456752
Change-Id: Idf9aa654aa0d66673f300f2f5425f0716d6c3e14
diff --git a/quic/test_tools/quic_transport_test_tools.h b/quic/test_tools/quic_transport_test_tools.h
index bf2dc0e..c6a8b46 100644
--- a/quic/test_tools/quic_transport_test_tools.h
+++ b/quic/test_tools/quic_transport_test_tools.h
@@ -23,6 +23,13 @@
   MOCK_METHOD1(CheckOrigin, bool(url::Origin));
 };
 
+class MockStreamVisitor : public QuicTransportStream::Visitor {
+ public:
+  MOCK_METHOD0(OnCanRead, void());
+  MOCK_METHOD0(OnFinRead, void());
+  MOCK_METHOD0(OnCanWrite, void());
+};
+
 }  // namespace test
 }  // namespace quic