GN: Refactor modules_unittests to eliminate package boundary violations.

webrtc/modules/pacing/BUILD.gn

Index: webrtc/modules/pacing/BUILD.gn
diff --git a/webrtc/modules/pacing/BUILD.gn b/webrtc/modules/pacing/BUILD.gn
index 09b856b9c9797522bf433049a136a8bc9fac3971..0a357c00d08574330b2a84bb8bd8f62ca213f3ed 100644
--- a/webrtc/modules/pacing/BUILD.gn
+++ b/webrtc/modules/pacing/BUILD.gn
@@ -32,3 +32,31 @@ rtc_static_library("pacing") {
     "../rtp_rtcp",
   ]
 }
+
+if (rtc_include_tests) {
+  rtc_source_set("pacing_unittests") {
+    testonly = true
+    sources = [
+      "alr_detector_unittest.cc",
+      "bitrate_prober_unittest.cc",
+      "paced_sender_unittest.cc",
+      "packet_router_unittest.cc",
+    ]
+    deps = [
+      ":pacing",
+      "../../base:rtc_base_approved",
+      "../../system_wrappers:system_wrappers",
+      "../../test:test_support",
+      "../rtp_rtcp",
+      "../rtp_rtcp:rtp_rtcp_unittests",
+      "//testing/gmock",
+    ]
+
+    # TODO(jschuh): bugs.webrtc.org/1348: fix this warning.
+    configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+    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" ]
+    }
+  }
+}