Reorganize net/disk_cache into backend specific directories.

net/disk_cache/v2/histogram_macros.h

Index: net/disk_cache/v2/histogram_macros.h
diff --git a/net/disk_cache/histogram_macros.h b/net/disk_cache/v2/histogram_macros.h
similarity index 96%
rename from net/disk_cache/histogram_macros.h
rename to net/disk_cache/v2/histogram_macros.h
index 651bce96f2de8fbc2b0010a83c14f82ec383d9cb..b70cfbb8f66fc0566b9dd6677e0d76583ef58319 100644
--- a/net/disk_cache/histogram_macros.h
+++ b/net/disk_cache/v2/histogram_macros.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_HISTOGRAM_MACROS_H_
-#define NET_DISK_CACHE_HISTOGRAM_MACROS_H_
+#ifndef NET_DISK_CACHE_V2_HISTOGRAM_MACROS_H_
+#define NET_DISK_CACHE_V2_HISTOGRAM_MACROS_H_
 
 // -----------------------------------------------------------------------------
 
@@ -84,7 +84,7 @@
 #define CACHE_HISTOGRAM_CACHE_ERROR(name, sample) \
     CACHE_HISTOGRAM_ENUMERATION(name, sample, 50)
 
-#ifdef NET_DISK_CACHE_BACKEND_IMPL_CC_
+#ifdef NET_DISK_CACHE_V2_BACKEND_IMPL_CC_
 #define BACKEND_OBJ this
 #else
 #define BACKEND_OBJ backend_
@@ -124,4 +124,4 @@
     }\
   }
 
-#endif  // NET_DISK_CACHE_HISTOGRAM_MACROS_H_
+#endif  // NET_DISK_CACHE_V2_HISTOGRAM_MACROS_H_