Loosening the coupling between WebRTC and //third_party/protobuf

webrtc/base/BUILD.gn

Index: webrtc/base/BUILD.gn
diff --git a/webrtc/base/BUILD.gn b/webrtc/base/BUILD.gn
index 3d0a3f42f1c113680b68e401bc3b9ae6f7a79628..dd3b45628c7b4b5c3d5e1ffe900717188f1ad645 100644
--- a/webrtc/base/BUILD.gn
+++ b/webrtc/base/BUILD.gn
@@ -79,6 +79,17 @@ if (!rtc_build_ssl) {
   }
 }
 
+source_set("protobuf_utils") {
+  sources = [
+    "protobuf_utils.h",
+  ]
+  if (rtc_enable_protobuf) {
+    public_deps = [
+      "//third_party/protobuf:protobuf_lite",
+    ]
+  }
+}
+
 # The subset of rtc_base approved for use outside of libjingle.
 rtc_static_library("rtc_base_approved") {
   defines = []