GN: Tighten up test target visibility + refactorings

webrtc/modules/desktop_capture/BUILD.gn

Index: webrtc/modules/desktop_capture/BUILD.gn
diff --git a/webrtc/modules/desktop_capture/BUILD.gn b/webrtc/modules/desktop_capture/BUILD.gn
index f8d52934051c5c4ede47601bea55be42ed2f26ff..748c46ae52dbaaa89a96906e7cf46e41c4f5cb7a 100644
--- a/webrtc/modules/desktop_capture/BUILD.gn
+++ b/webrtc/modules/desktop_capture/BUILD.gn
@@ -35,6 +35,9 @@ rtc_static_library("primitives") {
 if (rtc_include_tests) {
   rtc_source_set("desktop_capture_modules_tests") {
     testonly = true
+    if (!is_android && !is_ios) {  # Generated targets makes this check break.
+      visibility = [ "//webrtc/modules:modules_tests" ]
+    }
     sources = []
     deps = []
     if (rtc_desktop_capture_supported) {
@@ -57,6 +60,9 @@ if (rtc_include_tests) {
 
   rtc_source_set("desktop_capture_unittests") {
     testonly = true
+    if (!is_android && !is_ios) {  # Generated targets makes this check break.
+      visibility = [ "//webrtc/modules:modules_unittests" ]
+    }
     sources = [
       "blank_detector_desktop_capturer_wrapper_unittest.cc",
       "desktop_and_cursor_composer_unittest.cc",