Tracking mock_process_thread with a GN target

include/mock/mock_process_thread.h was not tracked by GN.

This cl creates a target for it. The target is testonly because it
depends on "webrtc/test:rtp_test_utils".

This means that dependencies to this header cannot fly under the
GN radar anymore. :)

BUG=webrtc:7652
NOTRY=True

Review-Url: https://codereview.webrtc.org/2881343003
Cr-Commit-Position: refs/heads/master@{#19234}

webrtc/call/BUILD.gn

@@ -158,6 +158,7 @@ if (rtc_include_tests) {
       "../modules/pacing",
       "../modules/rtp_rtcp",
       "../modules/rtp_rtcp:mock_rtp_rtcp",
+      "../modules/utility:mock_process_thread",
       "../rtc_base:rtc_base_approved",
       "../system_wrappers",
       "../test:audio_codec_mocks",

webrtc/modules/utility/BUILD.gn

@@ -40,6 +40,18 @@ rtc_static_library("utility") {
   ]
 }
 
+rtc_source_set("mock_process_thread") {
+  testonly = true
+  sources = [
+    "include/mock/mock_process_thread.h",
+  ]
+  deps = [
+    ":utility",
+    "../../rtc_base:rtc_base_approved",
+    "../../test:test_support",
+  ]
+}
+
 if (rtc_include_tests) {
   rtc_source_set("utility_unittests") {
     testonly = true

webrtc/video/BUILD.gn

@@ -277,6 +277,7 @@ if (rtc_include_tests) {
       "../modules/rtp_rtcp",
       "../modules/rtp_rtcp:mock_rtp_rtcp",
       "../modules/utility",
+      "../modules/utility:mock_process_thread",
       "../modules/video_coding",
       "../modules/video_coding:video_coding_utility",
       "../modules/video_coding:webrtc_h264",