GN: Refactor modules_unittests to eliminate package boundary violations.

webrtc/modules/audio_conference_mixer/BUILD.gn

Index: webrtc/modules/audio_conference_mixer/BUILD.gn
diff --git a/webrtc/modules/audio_conference_mixer/BUILD.gn b/webrtc/modules/audio_conference_mixer/BUILD.gn
index 2792a656e08bd521a6648a0ce81304531c6786a9..3c6f3d34d7b68a497cb13bbe5227feee48d289c9 100644
--- a/webrtc/modules/audio_conference_mixer/BUILD.gn
+++ b/webrtc/modules/audio_conference_mixer/BUILD.gn
@@ -46,3 +46,21 @@ rtc_static_library("audio_conference_mixer") {
     "../audio_processing",
   ]
 }
+
+if (rtc_include_tests) {
+  rtc_source_set("audio_conference_mixer_unittests") {
+    testonly = true
+    sources = [
+      "test/audio_conference_mixer_unittest.cc",
+    ]
+    deps = [
+      ":audio_conference_mixer",
+      "../../test:test_support",
+      "//testing/gmock",
+    ]
+    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" ]
+    }
+  }
+}