Initialize the simple cache backend at runtime.

net/disk_cache/disk_cache.h

Index: net/disk_cache/disk_cache.h
===================================================================
--- net/disk_cache/disk_cache.h	(revision 188696)
+++ net/disk_cache/disk_cache.h	(working copy)
@@ -54,6 +54,22 @@
                                   net::NetLog* net_log, Backend** backend,
                                   const net::CompletionCallback& callback);
 
+// A version of the above with additional |flags| allowing more fine-tuned
+// testing.
+int CreateCacheBackendWithFlags(net::CacheType type,
+                                const base::FilePath& path,
+                                int max_bytes,
+                                bool force,
+                                uint32 flags,
+                                base::MessageLoopProxy* thread,
+                                net::NetLog* net_log,
+                                Backend** backend,
+                                const net::CompletionCallback& callback);
+
+// Renames cache directory synchronously and fires off a background cleanup
+// task. Used by cache creator itself or by backends for self-restart on error.
+bool DelayedCacheCleanup(const base::FilePath& full_path);
+
 // The root interface for a disk cache instance.
 class NET_EXPORT Backend {
  public: