Inform disk cache of WebKit memory cache hits.

net/disk_cache/disk_cache.h

Index: net/disk_cache/disk_cache.h
diff --git a/net/disk_cache/disk_cache.h b/net/disk_cache/disk_cache.h
index 973b6e61a507b1be1d97707eb744ef8a33dc2366..03af1bcbdc9543385523ddbd9e86fd81c157bd2e 100644
--- a/net/disk_cache/disk_cache.h
+++ b/net/disk_cache/disk_cache.h
@@ -137,6 +137,11 @@ class NET_API Backend {
   // Return a list of cache statistics.
   virtual void GetStats(
       std::vector<std::pair<std::string, std::string> >* stats) = 0;
+
+  // Improves the rank of the specified resource in the LRU cache as if it had
+  // been used directly. This allows feedback from the renderer's memory cache

[rvargas (doing something else), 2011/07/28 22:27:01]

There should not be a reference to the renderer's memory cache here.

Also, stating that there is an LRU cache is not a good idea, because in fact the
default cache is not LRU... and what does it means to improve the rank of a
resource? That is an implementation detail.

We should just limit the documentation to the invariant part: That this method
should be called whenever there is an  external cache that is serving this entry
and we expect that entry to be stored by this cache. What we do with that
information is implementation specific.

+  // to improve the selection of resources in the disk cache.
+  virtual void OnExternalCacheHit(const std::string& key) = 0;
 };
 
 // This interface represents an entry in the disk cache.