Define XHR_RESPONSE_BLOB when building.

build/features_override.gypi

 # Copyright (c) 2009 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 file is only included in full-chromium builds, and overrides the
 # feature_defines variable in third_party/WebKit/WebKit/chromium/features.gypi.
 {
   'variables': {
     # WARNING: This list of strings completely replaces the list in
     # features.gypi. Therefore, if an enable is listed in features.gypi
@@ skipping 33 matching lines @@
       'ENABLE_SVG_AS_IMAGE=<(enable_svg)',
       'ENABLE_SVG_FONTS=<(enable_svg)',
       'ENABLE_SVG_FOREIGN_OBJECT=<(enable_svg)',
       'ENABLE_SVG_USE=<(enable_svg)',
       'ENABLE_TOUCH_EVENTS=<(enable_touch_events)',
       'ENABLE_V8_SCRIPT_DEBUG_SERVER=1',
       'ENABLE_VIDEO=1',
       'ENABLE_WEB_SOCKETS=1',
       'ENABLE_WEB_TIMING=1',
       'ENABLE_WORKERS=1',
+      'ENABLE_XHR_RESPONSE_BLOB=1',
       'ENABLE_XPATH=1',
       'ENABLE_XSLT=1',
     ],
     # We have to nest variables inside variables so that they can be overridden
     # through GYP_DEFINES.
     'variables': {
       'use_accelerated_compositing%': 1,
       'enable_svg%': 1,
       'enable_touch_events%': 1,
     },
@@ skipping 15 matching lines @@
     # require changes in gyp.
   },
 
 }
 
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