Move android_webview_build variable to toolchain.gypi to fix arm builders.

build/android.gypi

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 17 matching lines @@
 # Definitions for building standalone V8 binaries to run on Android.
 # This is mostly excerpted from:
 # http://src.chromium.org/viewvc/chrome/trunk/src/build/common.gypi
 
 {
   'variables': {
     # Location of Android NDK.
     'variables': {
       'android_ndk_root%': '<!(/bin/echo -n $ANDROID_NDK_ROOT)',
       'android_toolchain%': '<!(/bin/echo -n $ANDROID_TOOLCHAIN)',
-      # This is set when building the Android WebView inside the Android build
-      # system, using the 'android' gyp backend.
-      'android_webview_build%': 0,
     },
     'conditions': [
       ['android_ndk_root==""', {
         'variables': {
           'android_sysroot': '<(android_toolchain)/sysroot/',
           'android_stlport': '<(android_toolchain)/sources/cxx-stl/stlport/',
         },
         'android_include': '<(android_sysroot)/usr/include',
         'android_lib': '<(android_sysroot)/usr/lib',
         'android_stlport_include': '<(android_stlport)/stlport',
@@ skipping 219 matching lines @@
         'ldflags!': [
           '-Wl,-z,noexecstack',
           '-Wl,--gc-sections',
           '-Wl,-O1',
           '-Wl,--as-needed',
         ],
       }],
     ],  # target_conditions
   },  # target_defaults
 }