Enabling 'gn check' on webrtc/test.

webrtc/modules/audio_device/BUILD.gn

Index: webrtc/modules/audio_device/BUILD.gn
diff --git a/webrtc/modules/audio_device/BUILD.gn b/webrtc/modules/audio_device/BUILD.gn
index ab0b4f5b32f15b1b14606a5c098b0c9dbbf04d76..95c2f13171c44b1a0aad83d54bd0b415eacab3a4 100644
--- a/webrtc/modules/audio_device/BUILD.gn
+++ b/webrtc/modules/audio_device/BUILD.gn
@@ -253,6 +253,19 @@ config("mock_audio_device_config") {
   }
 }
 
+rtc_source_set("mock_audio_device") {
+  testonly = true
+  sources = [
+    "include/mock_audio_device.h",
+    "include/mock_audio_transport.h",
+  ]
+  deps = [
+    ":audio_device",
+    "../../test:test_support",
+  ]
+  all_dependent_configs = [ ":mock_audio_device_config" ]
+}
+
 if (rtc_include_tests) {
   rtc_source_set("audio_device_unittests") {
     testonly = true
@@ -308,19 +321,6 @@ if (rtc_include_tests) {
     }
   }
 
-  rtc_source_set("mock_audio_device") {
-    testonly = true
-    sources = [
-      "include/mock_audio_device.h",
-      "include/mock_audio_transport.h",
-    ]
-    deps = [
-      ":audio_device",
-      "../../test:test_support",
-    ]
-    all_dependent_configs = [ ":mock_audio_device_config" ]
-  }
-
   if (!is_ios) {
     # These tests do not work on ios, see
     # https://bugs.chromium.org/p/webrtc/issues/detail?id=4755