Use a single cros_toolchain tarball for ChromeOS build

gyp/common.gypi

 # Copyright 2011 The Android Open Source Project
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # This file is automatically included by gyp_skia when building any target.
 
 {
   'includes': [
     'common_variables.gypi',
   ],
 
   'target_defaults': {
     'defines': [
       'SK_GAMMA_SRGB',
       'SK_GAMMA_APPLY_TO_A8',
     ],
 
     # Validate the 'skia_os' setting against 'OS', because only certain
     # combinations work.  You should only override 'skia_os' for certain
     # situations, like building for iOS on a Mac.
     'variables': {
       'conditions': [
         [ 'skia_os != OS and not ((skia_os == "ios" and OS == "mac") or \
-                                  (skia_os == "nacl" and OS == "linux"))', {
+                                  (skia_os == "nacl" and OS == "linux") or \
+                                  (skia_os == "chromeos" and OS == "linux"))', {
           'error': '<!(Cannot build with skia_os=<(skia_os) on OS=<(OS))',
         }],
         [ 'skia_mesa and skia_os not in ["mac", "linux"]', {
           'error': '<!(skia_mesa=1 only supported with skia_os="mac" or "linux".)',
         }],
         [ 'skia_angle and not skia_os == "win"', {
           'error': '<!(skia_angle=1 only supported with skia_os="win".)',
         }],
         [ 'skia_arch_width != 32 and skia_arch_width != 64', {
           'error': '<!(skia_arch_width can only be 32 or 64 bits not <(skia_arch_width) bits)',
         }],
         [ 'skia_os == "nacl" and OS != "linux"', {
           'error': '<!(Skia NaCl build only currently supported on Linux.)',
         }],
         [ 'skia_os == "chromeos" and OS != "linux"', {
           'error': '<!(Skia ChromeOS build is only supported on Linux.)',
         }],
-        [ 'skia_os == "chromeos" and not skia_cros_target', {
-          'error': '<!(skia_cros_target must be defined for ChromeOS)',
-        }],
       ],
     },
     'includes': [
       'common_conditions.gypi',
     ],
     'conditions': [
       [ 'skia_scalar == "float"',
         {
           'defines': [
             'SK_SCALAR_IS_FLOAT',
@@ skipping 55 matching lines @@
         ],
       },
     },
   }, # end 'target_defaults'
 }
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