Reland "Enable and fix chromium clang warnings in rtp_rtcp test targets"

This reverts commit 01aa210fad68f1006528d32d388b307c22990734.

Reason for revert: downstream project adjusted

Original change's description:
> Revert "Enable and fix chromium clang warnings in rtp_rtcp test targets"
> 
> This reverts commit 9486b117daac09c9f7ac8450ccda835938cf3150.
> 
> Reason for revert: Breaks downstream project
> 
> Original change's description:
> > Enable and fix chromium clang warnings in rtp_rtcp test targets
> > 
> > Bug: webrtc:163
> > Change-Id: I4ed3e63296d8bf06536a83196d597c7a906ba11c
> > Reviewed-on: https://webrtc-review.googlesource.com/60802
> > Reviewed-by: Björn Terelius <terelius@webrtc.org>
> > Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
> > Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
> > Cr-Commit-Position: refs/heads/master@{#22357}
> 
> TBR=danilchap@webrtc.org,phoglund@webrtc.org,terelius@webrtc.org
> 
> Change-Id: I2c3777ea9f26813bdb395e7fd68f6b49443586ea
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: webrtc:163
> Reviewed-on: https://webrtc-review.googlesource.com/61060
> Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
> Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#22365}

TBR=danilchap@webrtc.org,phoglund@webrtc.org,oprypin@webrtc.org,terelius@webrtc.org

Change-Id: I0b4cb6d05b37caeb52cca9abf95417ad3ad6f76b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:163
Reviewed-on: https://webrtc-review.googlesource.com/61080
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22368}
diff --git a/test/BUILD.gn b/test/BUILD.gn
index 409be1a1..b4b1277 100644
--- a/test/BUILD.gn
+++ b/test/BUILD.gn
@@ -567,6 +567,7 @@
     "fake_videorenderer.h",
     "layer_filtering_transport.cc",
     "layer_filtering_transport.h",
+    "mock_transport.cc",
     "mock_transport.h",
     "null_transport.cc",
     "null_transport.h",