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

BUILD.gn

 # Copyright (c) 2013 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 152 matching lines @@
 
   if (is_win) {
     deps += [ "//ui/metro_viewer" ]
   }
 
   if (is_win || is_mac || is_chromeos) {
     # RLZ works on these platforms.
     deps += [ "//rlz:rlz_lib" ]
   }
 
-  if (cpu_arch == "x86" || cpu_arch == "x64") {
+  if (current_cpu == "x86" || current_cpu == "x64") {
     # YASM is x86/x64 only.
     deps += [ "//third_party/yasm($host_toolchain)" ]
   }
 
   if (is_android) {
     deps += [
       "//base/android/linker:chromium_android_linker",
       "//build/android/gyp/test:hello_world",
       "//build/android/rezip",
       "//third_party/openmax_dl/dl",
@@ skipping 111 matching lines @@
       "//ui/views",
       "//ui/views/controls/webview",
       "//ui/web_dialogs",
     ]
   }
 
   if (is_mac || is_ios) {
     deps -= [ "//ui/touch_selection" ]
   }
 }