Move enable_webrtc to a buildflag header.

gpu/command_buffer/service/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/config/ui.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 group("service") {
   if (is_component_build) {
     public_deps = [
@@ skipping 148 matching lines @@
   ]
   deps = [
     ":disk_cache_proto",
     "//base",
     "//base/third_party/dynamic_annotations",
     "//crypto",
     "//gpu/command_buffer/client:client_sources",
     "//gpu/command_buffer/common:gles2_utils",
     "//gpu/config:config_sources",
     "//gpu/ipc/common:surface_handle_type",
+    "//media:media_features",
     "//third_party/angle:angle_image_util",
     "//third_party/angle:commit_id",
     "//third_party/angle:translator",
     "//third_party/protobuf:protobuf_lite",
     "//third_party/re2",
     "//third_party/smhasher:cityhash",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
     "//ui/gl/init",
@@ skipping 12 matching lines @@
     configs -= [ "//build/config/compiler:default_optimization" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 }
 
 proto_library("disk_cache_proto") {
   sources = [
     "disk_cache_proto.proto",
   ]
 }