Move enable_webrtc to a buildflag header.

components/nacl/loader/BUILD.gn

 # Copyright 2015 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/features.gni")
 import("//build/config/nacl/config.gni")
 import("//testing/test.gni")
 
 assert(enable_nacl)
 
@@ skipping 37 matching lines @@
 source_set("minimal_content_dummy") {
   check_includes = false
   sources = [
     "//content/public/common/child_process_sandbox_support_linux.h",
     "//content/public/common/content_descriptors.h",
     "//content/public/common/content_switches.h",
     "//content/public/common/main_function_params.h",
     "//content/public/common/mojo_channel_switches.h",
     "//content/public/common/sandbox_init.h",
   ]
+
+  # Deps required by the above headers.
+  deps = [
+    "//media:media_features",
+  ]
 }
 
 source_set("loader") {
   public_deps = [
     ":minimal",
   ]
   deps = [
     "//components/nacl/common",
     "//content/public/common",
     "//ppapi/shared_impl",
@@ skipping 215 matching lines @@
       "${root_out_dir}/nacl_helper_nonsfi_unittests_main",
     ]
     outputs = [
       "${root_build_dir}/{{source_file_part}}",
     ]
     deps = [
       ":nacl_helper_nonsfi_unittests_main",
     ]
   }
 }