Move enable_webrtc to a buildflag header.

chrome/common/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/buildflag_header.gni")
 import("//build/util/process_version.gni")
 import("//chrome/common/features.gni")
 import("//chrome/process_version_rc_template.gni")  # For branding_file_path.
 import("//extensions/features/features.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
@@ skipping 563 matching lines @@
     "//extensions/features",
     "//printing/features",
   ]
   deps = [
     ":version_header",
     "//base",
     "//base/third_party/dynamic_annotations",
     "//components/bookmarks/common",
     "//components/nacl/common:switches",
     "//media:cdm_paths",  # Needed by chrome_paths.cc.
+    "//media:media_features",
     "//ppapi/features",
     "//third_party/widevine/cdm:headers",
   ]
 
   if (is_android) {
     # This dependency must only be added for Android.
     #
     # On Windows, //chrome/installer/util depends on this target to get
     # constants. That target is in turn used in a number of installer helper
     # targets independent of Chrome that we want to keep small. So we don't
@@ skipping 74 matching lines @@
   sources = [
     "network_diagnostics.mojom",
     "resource_usage_reporter.mojom",
     "shell_handler_win.mojom",
   ]
 
   public_deps = [
     "//url/mojo:url_mojom_gurl",
   ]
 }