GN: Use rtc_include_tests variable to exclude tests.

This is closer to what the GYP build does, and is more readable.

BUG=webrtc:5949
TBR=phoglund@webrtc.org
NOTRY=True

Review-Url: https://codereview.webrtc.org/2043873003
Cr-Commit-Position: refs/heads/master@{#13054}

build_overrides/webrtc.gni

@@ -22,3 +22,6 @@ rtc_include_pulse_audio = true
 # Chromium uses its own IO handling, so the internal ADM is only built for
 # standalone WebRTC.
 rtc_include_internal_audio_device = true
+
+# There's no point processing WebRTC standalone tests in a Chromium build.
+rtc_include_tests = true

webrtc/BUILD.gn

@@ -379,8 +379,7 @@ if (use_libfuzzer || use_drfuzz) {
   }
 }
 
-# There's no point processing WebRTC standalone tests in a Chromium build.
-if (!build_with_chromium) {
+if (!rtc_include_tests) {
   config("rtc_unittests_config") {
     # GN orders flags on a target before flags from configs. The default config
     # adds -Wall, and this flag have to be after -Wall -- so they need to

webrtc/base/BUILD.gn

@@ -632,8 +632,7 @@ source_set("gtest_prod") {
   ]
 }
 
-# There's no point processing WebRTC standalone tests in a Chromium build.
-if (!build_with_chromium) {
+if (!rtc_include_tests) {
   config("rtc_base_test_utils_exported_config") {
     defines = [ "GTEST_RELATIVE_PATH" ]
   }

webrtc/system_wrappers/BUILD.gn

@@ -193,8 +193,7 @@ if (is_linux) {
   }
 }
 
-# There's no point processing WebRTC standalone tests in a Chromium build.
-if (!build_with_chromium) {
+if (!rtc_include_tests) {
   test("system_wrappers_unittests") {
     testonly = true
     sources = [

webrtc/tools/BUILD.gn

@@ -170,8 +170,7 @@ source_set("agc_test_utils") {
 }
 
 # Exclude tools depending on gflags since that's not available in Chromium.
-# There's no point processing WebRTC standalone tests in a Chromium build.
-if (!build_with_chromium) {
+if (!rtc_include_tests) {
   executable("agc_harness") {
     testonly = true
     sources = [