Fix building gpu twice in gn component build

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 = [
       "//gpu",
     ]
   } else {
     public_deps = [
       ":service_sources",
     ]
   }
 }
 
 source_set("service_sources") {
   visibility = [
-    "//content/public/gpu/*",
     "//gpu/*",
     "//mojo/gles2:gles2",
   ]
 
   sources = [
     "buffer_manager.cc",
     "buffer_manager.h",
     "cmd_buffer_engine.h",
     "cmd_parser.cc",
     "cmd_parser.h",
@@ skipping 139 matching lines @@
     configs -= [ "//build/config/compiler:default_optimization" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 }
 
 proto_library("disk_cache_proto") {
   sources = [
     "disk_cache_proto.proto",
   ]
 }