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

net/net.gyp

Index: net/net.gyp
diff --git a/net/net.gyp b/net/net.gyp
index f82c13216368d2eb30d0e7dffe79d8bad354bbed..b264ca5527ac6a398ddec17466f7c9db0312059c 100644
--- a/net/net.gyp
+++ b/net/net.gyp
@@ -7,6 +7,7 @@
     '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"', {
@@ -1287,11 +1288,69 @@
             'dns/dns_client.cc',
           ],
         }],
+	['use_blockfile_cache_backend==1', {
+	  'defines': [
+	    'USE_BLOCKFILE_CACHE_BACKEND',
+	  ],
+	}, { # use_blockfile_cache_backend == 0
+	  'sources!': [
+            'disk_cache/blockfile/addr.cc',
+            'disk_cache/blockfile/addr.h',
+            'disk_cache/blockfile/backend_impl.cc',
+            'disk_cache/blockfile/backend_impl.h',
+            'disk_cache/blockfile/bitmap.cc',
+            'disk_cache/blockfile/bitmap.h',
+            'disk_cache/blockfile/block_files.cc',
+            'disk_cache/blockfile/block_files.h',
+            'disk_cache/blockfile/disk_format.cc',
+            'disk_cache/blockfile/disk_format.h',
+            'disk_cache/blockfile/disk_format_base.h',
+            'disk_cache/blockfile/entry_impl.cc',
+            'disk_cache/blockfile/entry_impl.h',
+            'disk_cache/blockfile/errors.h',
+            'disk_cache/blockfile/eviction.cc',
+            'disk_cache/blockfile/eviction.h',
+            'disk_cache/blockfile/experiments.h',
+            'disk_cache/blockfile/file.cc',
+            'disk_cache/blockfile/file.h',
+            'disk_cache/blockfile/file_block.h',
+            'disk_cache/blockfile/file_lock.cc',
+            'disk_cache/blockfile/file_lock.h',
+            'disk_cache/blockfile/file_posix.cc',
+            'disk_cache/blockfile/file_win.cc',
+            'disk_cache/blockfile/histogram_macros.h',
+            'disk_cache/blockfile/in_flight_backend_io.cc',
+            'disk_cache/blockfile/in_flight_backend_io.h',
+            'disk_cache/blockfile/in_flight_io.cc',
+            'disk_cache/blockfile/in_flight_io.h',
+            'disk_cache/blockfile/mapped_file.cc',
+            'disk_cache/blockfile/mapped_file.h',
+            'disk_cache/blockfile/mapped_file_posix.cc',
+            'disk_cache/blockfile/mapped_file_avoid_mmap_posix.cc',
+            'disk_cache/blockfile/mapped_file_win.cc',
+            'disk_cache/blockfile/rankings.cc',
+            'disk_cache/blockfile/rankings.h',
+            'disk_cache/blockfile/sparse_control.cc',
+            'disk_cache/blockfile/sparse_control.h',
+            'disk_cache/blockfile/stats.cc',
+            'disk_cache/blockfile/stats.h',
+            'disk_cache/blockfile/stats_histogram.cc',
+            'disk_cache/blockfile/stats_histogram.h',
+            'disk_cache/blockfile/storage_block-inl.h',
+            'disk_cache/blockfile/storage_block.h',
+            'disk_cache/blockfile/stress_support.h',
+            'disk_cache/blockfile/trace.cc',
+            'disk_cache/blockfile/trace.h',
+            'disk_cache/blockfile/v3/block_bitmaps.cc',
+            'disk_cache/blockfile/v3/block_bitmaps.h',
+            'disk_cache/blockfile/v3/disk_format_v3.h',
+	  ],
+        }],
         ['use_tracing_cache_backend==1', {
           'defines': [
             'USE_TRACING_CACHE_BACKEND'
           ],
-         }],
+        }],
         ['use_openssl==1', {
             'sources!': [
               'base/crypto_module_nss.cc',