Update Chomium's build files to work w/ latest GN binaries.

content/gpu/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("//content/content.gni")
 
 source_set("gpu") {
   visibility = [ "//content/*" ]
 
@@ skipping 25 matching lines @@
       "//third_party/khronos:khronos_headers",
       "//third_party/wtl:wtl_includes",
     ]
     libs = [ "setupapi.lib" ]
     deps += [
       "//third_party/angle:libEGL",
       "//third_party/angle:libGLESv2",
     ]
   }
 
-  if (is_chromeos && cpu_arch != "arm") {
+  if (is_chromeos && current_cpu != "arm") {
     configs += [ "//third_party/libva:libva_config" ]
   }
 
   if (use_x11) {
     deps += [ "//ui/events/platform/x11" ]
   }
 }