Reorganize net/disk_cache into backend specific directories.

net/disk_cache/blockfile/histogram_macros_v3.h

Index: net/disk_cache/blockfile/histogram_macros_v3.h
diff --git a/net/disk_cache/v3/histogram_macros.h b/net/disk_cache/blockfile/histogram_macros_v3.h
similarity index 96%
rename from net/disk_cache/v3/histogram_macros.h
rename to net/disk_cache/blockfile/histogram_macros_v3.h
index 99a9cbe5ca5e0a1eb28e9245cd460079093010f0..5720d3a2f0f50d47148a866ffdc97e52e9c2e6cf 100644
--- a/net/disk_cache/v3/histogram_macros.h
+++ b/net/disk_cache/blockfile/histogram_macros_v3.h
@@ -8,8 +8,8 @@
 // keeping track of a potentially large number of histogram objects that have to
 // survive the backend object that created them.
 
-#ifndef NET_DISK_CACHE_V3_HISTOGRAM_MACROS_H_
-#define NET_DISK_CACHE_V3_HISTOGRAM_MACROS_H_
+#ifndef NET_DISK_CACHE_BLOCKFILE_HISTOGRAM_MACROS_V3_H_
+#define NET_DISK_CACHE_BLOCKFILE_HISTOGRAM_MACROS_V3_H_
 
 // -----------------------------------------------------------------------------
 
@@ -117,4 +117,4 @@
     }\
   }
 
-#endif  // NET_DISK_CACHE_V3_HISTOGRAM_MACROS_H_
+#endif  // NET_DISK_CACHE_BLOCKFILE_HISTOGRAM_MACROS_V3_H_