hide Config in SkImageDecoder -- use SkColorType instead

gyp/skia_for_android_framework_defines.gypi

 # Copyright 2014 Google Inc.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This file is included by chrome's skia/skia_common.gypi, and is intended to
 # augment the skia flags that are set there.
 
 {
   'variables': {
 
     # These flags will be defined in the android framework.
     #
     # If these become 'permanent', they should be moved into common_variables.gypi
     #
     'skia_for_android_framework_defines': [
       'SK_SUPPORT_LEGACY_SETCONFIG_INFO',
       'SK_SUPPORT_LEGACY_SETCONFIG',
+      'SK_SUPPORT_LEGACY_IMAGEDECODER_CONFIG',
       # Needed until we fix skbug.com/2440.
       'SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG',
       # Transitional, for deprecated SkCanvas::SaveFlags methods.
       'SK_ATTR_DEPRECATED=SK_NOTHING_ARG1',
       'SK_SUPPORT_LEGACY_SHADER_LOCALMATRIX',
       'SK_SUPPORT_LEGACY_COMPUTE_CONFIG_SIZE',
     ],
   },
 }