Http cache: Implement a timeout for the cache lock.

net/http/http_cache.h

Index: net/http/http_cache.h
diff --git a/net/http/http_cache.h b/net/http/http_cache.h
index 732a9c09c75b03e5664c0b1f5f73e7a9388a547b..752b98a6715b0f9c66030d4a9e143fb90d9b522e 100644
--- a/net/http/http_cache.h
+++ b/net/http/http_cache.h
@@ -187,6 +187,12 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
   // Initializes the Infinite Cache, if selected by the field trial.
   void InitializeInfiniteCache(const base::FilePath& path);
 
+  // Causes all transactions created after this point to effectively bypass
+  // the cache lock whenever there is lock contention.
+  void BypassLockForTest() {
+    bypass_lock_for_test_ = true;
+  }
+
   // HttpTransactionFactory implementation:
   virtual int CreateTransaction(RequestPriority priority,
                                 scoped_ptr<HttpTransaction>* trans) OVERRIDE;
@@ -389,6 +395,7 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
   // Used when lazily constructing the disk_cache_.
   scoped_ptr<BackendFactory> backend_factory_;
   bool building_backend_;
+  bool bypass_lock_for_test_;
 
   Mode mode_;