Disk cache: Add stress_support.h to net.gyp

This was missing from r106538

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/8437011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@108171 0039d316-1c4b-4281-b951-d872f2087c98

net/net.gyp

@@ -308,6 +308,7 @@
         'disk_cache/stats_histogram.h',
         'disk_cache/storage_block-inl.h',
         'disk_cache/storage_block.h',
+        'disk_cache/stress_support.h',
         'disk_cache/trace.cc',
         'disk_cache/trace.h',
         'dns/async_host_resolver.cc',