Reorganize net/disk_cache into backend specific directories.

net/disk_cache/memory/mem_backend_impl.cc

Index: net/disk_cache/memory/mem_backend_impl.cc
diff --git a/net/disk_cache/mem_backend_impl.cc b/net/disk_cache/memory/mem_backend_impl.cc
similarity index 98%
rename from net/disk_cache/mem_backend_impl.cc
rename to net/disk_cache/memory/mem_backend_impl.cc
index ccd868b65304130980a0e06c41d0513b13217b27..e69c00edf636a45379a7f29db182512dd8a67c36 100644
--- a/net/disk_cache/mem_backend_impl.cc
+++ b/net/disk_cache/memory/mem_backend_impl.cc
@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "net/disk_cache/mem_backend_impl.h"
+#include "net/disk_cache/memory/mem_backend_impl.h"
 
 #include "base/logging.h"
 #include "base/sys_info.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/cache_util.h"
-#include "net/disk_cache/mem_entry_impl.h"
+#include "net/disk_cache/memory/mem_entry_impl.h"
 
 using base::Time;