Replace QuicheStringPiece with absl::string_view

Tested:
    TAP train for global presubmit queue
    http://test/OCL:335945871:BASE:336020766:1602159631460:96037042
PiperOrigin-RevId: 336093514
Change-Id: I27c7455ff096f2f0d6d8166c312f066b902cb234
diff --git a/quic/test_tools/quic_transport_test_tools.h b/quic/test_tools/quic_transport_test_tools.h
index 50db80a..ba0cc39 100644
--- a/quic/test_tools/quic_transport_test_tools.h
+++ b/quic/test_tools/quic_transport_test_tools.h
@@ -17,10 +17,7 @@
   MOCK_METHOD(void, OnSessionReady, (), (override));
   MOCK_METHOD(void, OnIncomingBidirectionalStreamAvailable, (), (override));
   MOCK_METHOD(void, OnIncomingUnidirectionalStreamAvailable, (), (override));
-  MOCK_METHOD(void,
-              OnDatagramReceived,
-              (quiche::QuicheStringPiece),
-              (override));
+  MOCK_METHOD(void, OnDatagramReceived, (absl::string_view), (override));
   MOCK_METHOD(void, OnCanCreateNewOutgoingBidirectionalStream, (), (override));
   MOCK_METHOD(void, OnCanCreateNewOutgoingUnidirectionalStream, (), (override));
 };