Refactoring ./webrtc/modules/BUILD.gn for gn check

webrtc/modules/audio_coding/BUILD.gn

Index: webrtc/modules/audio_coding/BUILD.gn
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index 70ecc55dc2aa86d3f2739bdd6d91567fe112be17..1c762a232d16ee0e2dbb6b55434540a5d759b51a 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -540,7 +540,12 @@ rtc_static_library("isac") {
 }
 
 rtc_static_library("isac_c") {
-  visibility = [ ":*" ]  # Only targets in this file can depend on this.
+  # Only targets in this file should depend on this (or testing targets).
+  visibility = [
+    "//webrtc/modules:*",
+    ":*",
+  ]
+
   sources = [
     "codecs/isac/main/include/audio_decoder_isac.h",
     "codecs/isac/main/include/audio_encoder_isac.h",
@@ -808,7 +813,12 @@ rtc_static_library("pcm16b") {
 }
 
 rtc_source_set("pcm16b_c") {
-  visibility = [ ":*" ]  # Only targets in this file can depend on this.
+  # Only targets in this file should depend on this (or testing targets).
+  visibility = [
+    "//webrtc/modules:_modules_tests__library",
+    "//webrtc/modules:*",
+    ":*",
+  ]
   sources = [
     "codecs/pcm16b/pcm16b.c",
     "codecs/pcm16b/pcm16b.h",