Reland of Enable GN check for webrtc/base

webrtc/test/BUILD.gn

Index: webrtc/test/BUILD.gn
diff --git a/webrtc/test/BUILD.gn b/webrtc/test/BUILD.gn
index d7c1f8a4e494d36b1b48f829fb71dc91f40183e0..fe50aa95fea3d4f5084a604d4453bfa3268bdd55 100644
--- a/webrtc/test/BUILD.gn
+++ b/webrtc/test/BUILD.gn
@@ -172,14 +172,29 @@ rtc_source_set("video_test_support") {
   }
 }
 
+rtc_source_set("isolated_output") {
+  # This target was part of :test_support but it depends on //third_party/gflags
+  # and this can be a problem because test_support is pulled in from a target
+  # that is used by Chromium and they are not using gflags.
+  # Please do not merge this target with :test_support.
+  testonly = true
+  sources = [
+    "testsupport/isolated_output.cc",
+    "testsupport/isolated_output.h",
+  ]
+  deps = [
+    ":fileutils",
+    "../base:rtc_base_approved",
+    "//third_party/gflags",
+  ]
+}
+
 rtc_source_set("test_support") {
   testonly = true
 
   sources = [
     "gmock.h",
     "gtest.h",
-    "testsupport/isolated_output.cc",
-    "testsupport/isolated_output.h",
     "testsupport/packet_reader.cc",
     "testsupport/packet_reader.h",
     "testsupport/perf_test.cc",
@@ -189,14 +204,15 @@ rtc_source_set("test_support") {
     "testsupport/unittest_utils.h",
   ]
 
+  # Do not add a dependency on //third_party/gflags here because it breaks
+  # Chromium.
   deps = [
-    "../base:gtest_prod",
+    "..:webrtc_common",
     "../base:rtc_base_approved",
     "../common_video",
     "../system_wrappers",
     "//testing/gmock",
     "//testing/gtest",
-    "//third_party/gflags",
   ]
 
   public_deps = [
@@ -296,6 +312,7 @@ rtc_test("test_support_unittests") {
   deps += [
     ":direct_transport",
     ":fileutils_unittests",
+    ":isolated_output",
     ":test_common",
     ":test_main",
     ":video_test_common",