GN: Refactor modules_unittests to eliminate package boundary violations.

webrtc/modules/rtp_rtcp/BUILD.gn

Index: webrtc/modules/rtp_rtcp/BUILD.gn
diff --git a/webrtc/modules/rtp_rtcp/BUILD.gn b/webrtc/modules/rtp_rtcp/BUILD.gn
index 9b236218b3f986da9ca49d7ce3142958c2c7570f..111a24c9121ccc51c9df7904c73acac8d356ab9c 100644
--- a/webrtc/modules/rtp_rtcp/BUILD.gn
+++ b/webrtc/modules/rtp_rtcp/BUILD.gn
@@ -211,6 +211,22 @@ if (rtc_include_tests) {
     ]
   }  # test_packet_masks_metrics
 
+  rtc_source_set("rtp_rtcp_modules_tests") {
+    testonly = true
+    sources = [
+      "test/testFec/test_fec.cc",
+    ]
+    deps = [
+      ":rtp_rtcp",
+      "../../base:rtc_base_approved",
+      "../../test:test_support",
+    ]
+    if (!build_with_chromium && is_clang) {
+      # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
+      suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
+    }
+  }
+
   rtc_source_set("rtp_rtcp_unittests") {
     testonly = true
     sources = [