Reland of Loosening the coupling between WebRTC and //third_party/protobuf

webrtc/base/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
@@ skipping 61 matching lines @@
 }
 
 if (!rtc_build_ssl) {
   config("external_ssl_library") {
     assert(rtc_ssl_root != "",
            "You must specify rtc_ssl_root when rtc_build_ssl==0.")
     include_dirs = [ rtc_ssl_root ]
   }
 }
 
+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 = []
   libs = []
   deps = []
   all_dependent_configs = [ ":rtc_base_approved_all_dependent_config" ]
 
   sources = [
     "array_view.h",
     "arraysize.h",
@@ skipping 808 matching lines @@
 
 if (is_android) {
   android_library("base_java") {
     java_files = [
       "java/src/org/webrtc/Logging.java",
       "java/src/org/webrtc/Size.java",
       "java/src/org/webrtc/ThreadUtils.java",
     ]
   }
 }