Loosening the coupling between WebRTC and //third_party/protobuf

webrtc/modules/audio_processing/BUILD.gn

Index: webrtc/modules/audio_processing/BUILD.gn
diff --git a/webrtc/modules/audio_processing/BUILD.gn b/webrtc/modules/audio_processing/BUILD.gn
index 84f25b5e8ed7cfae29013af1fb8fba48e5805ef3..651c6b230ce5a04d2093cb40c929f0722885fc2b 100644
--- a/webrtc/modules/audio_processing/BUILD.gn
+++ b/webrtc/modules/audio_processing/BUILD.gn
@@ -232,6 +232,7 @@ rtc_static_library("audio_processing") {
     "../..:webrtc_common",
     "../../audio/utility:audio_frame_operations",
     "../../base:gtest_prod",
+    "../../base:protobuf_utils",
     "../audio_coding:isac",
   ]
   public_deps = [
@@ -523,6 +524,7 @@ if (rtc_include_tests) {
       ":audioproc_test_utils",
       "../..:webrtc_common",
       "../../base:gtest_prod",
+      "../../base:protobuf_utils",
       "../../base:rtc_base",
       "../../base:rtc_base_approved",
       "../../common_audio:common_audio",
@@ -661,6 +663,9 @@ if (rtc_include_tests) {
     } else {
       defines = [ "WEBRTC_INTELLIGIBILITY_ENHANCER=0" ]
     }
+
+    # TODO(mbonadei): remove this before landing this CL
+    include_dirs = [ "//third_party/protobuf/src" ]
   }
 
   if (rtc_enable_protobuf) {
@@ -815,6 +820,7 @@ if (rtc_include_tests) {
       deps = [
         ":audioproc_debug_proto",
         "../..:webrtc_common",
+        "../../base:protobuf_utils",
         "../../base:rtc_base_approved",
       ]
     }