Http cache: Implement a timeout for the cache lock.

net/http/mock_http_cache.cc

Index: net/http/mock_http_cache.cc
diff --git a/net/http/mock_http_cache.cc b/net/http/mock_http_cache.cc
index 5dbd486df0ff551c2dd6237e004edfab8d941df0..a91b2c1aa83107c737b67aa40ab064b1ef44f1f3 100644
--- a/net/http/mock_http_cache.cc
+++ b/net/http/mock_http_cache.cc
@@ -516,6 +516,10 @@ int MockHttpCache::CreateTransaction(scoped_ptr<net::HttpTransaction>* trans) {
   return http_cache_.CreateTransaction(net::DEFAULT_PRIORITY, trans);
 }
 
+void MockHttpCache::BypassCacheLock() {
+  http_cache_.BypassLockForTest();
+}
+
 bool MockHttpCache::ReadResponseInfo(disk_cache::Entry* disk_entry,
                                      net::HttpResponseInfo* response_info,
                                      bool* response_truncated) {