Make the blockfile cache an optional build product for chrome target.

net/net.gyp

 # Copyright 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.
 
 {
   'variables': {
     'chromium_code': 1,
 
     'linux_link_kerberos%': 0,
+    'use_blockfile_cache_backend%': 1,
     'use_tracing_cache_backend%': 0,
     'conditions': [
       ['chromeos==1 or embedded==1 or OS=="android" or OS=="ios"', {
         # Disable Kerberos on ChromeOS, Android and iOS, at least for now.
         # It needs configuration (krb5.conf and so on).
         'use_kerberos%': 0,
       }, {  # chromeos == 0 and embedded==0 and OS!="android" and OS!="ios"
         'use_kerberos%': 1,
       }],
       ['OS=="android" and target_arch != "ia32"', {
@@ skipping 1319 matching lines @@
           'defines': [
             'ENABLE_BUILT_IN_DNS',
           ]
         }, { # else
           'sources!': [
             'dns/address_sorter_posix.cc',
             'dns/address_sorter_posix.h',
             'dns/dns_client.cc',
           ],
         }],
+        ['use_blockfile_cache_backend==1', {
+          'defines': [
+            'USE_BLOCKFILE_CACHE_BACKEND',
+          ],
+        }, { # use_blockfile_cache_backend == 0
+          'sources/': [ ['exclude', '^disk_cache/blockfile/' ] ]
+        }],
         ['use_tracing_cache_backend==1', {
           'defines': [
             'USE_TRACING_CACHE_BACKEND'
           ],
-         }],
+        }],
         ['use_openssl==1', {
             'sources!': [
               'base/crypto_module_nss.cc',
               'base/keygen_handler_nss.cc',
               'base/nss_memio.c',
               'base/nss_memio.h',
               'cert/cert_database_nss.cc',
               'cert/cert_verify_proc_nss.cc',
               'cert/cert_verify_proc_nss.h',
               'cert/ct_log_verifier_nss.cc',
@@ skipping 1862 matching lines @@
             'net_unittests.isolate',
           ],
           'sources': [
             'net_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }