Remove disk_cache::BackendImpl::OpenPrevEntry() and all users.

net/disk_cache/blockfile/backend_impl_v3.h

Index: net/disk_cache/blockfile/backend_impl_v3.h
diff --git a/net/disk_cache/blockfile/backend_impl_v3.h b/net/disk_cache/blockfile/backend_impl_v3.h
index e438fdbe12a611c56a62feb4ce9137691d1ce177..b57bb8914e6a4a4600508588a14b90b526cdc064 100644
--- a/net/disk_cache/blockfile/backend_impl_v3.h
+++ b/net/disk_cache/blockfile/backend_impl_v3.h
@@ -55,10 +55,6 @@ class NET_EXPORT_PRIVATE BackendImplV3 : public Backend {
   // Performs general initialization for this current instance of the cache.
   int Init(const CompletionCallback& callback);
 
-  // Same behavior as OpenNextEntry but walks the list from back to front.
-  int OpenPrevEntry(void** iter, Entry** prev_entry,
-                    const CompletionCallback& callback);
-
   // Sets the maximum size for the total amount of data stored by this instance.
   bool SetMaxSize(int max_bytes);
 
@@ -216,10 +212,6 @@ class NET_EXPORT_PRIVATE BackendImplV3 : public Backend {
   // on failure.
   int NewEntry(Addr address, EntryImplV3** entry);
 
-  // Opens the next or previous entry on a cache iteration.
-  int OpenFollowingEntry(bool forward, void** iter, Entry** next_entry,
-                         const CompletionCallback& callback);
-
   // Handles the used storage count.
   void AddStorageSize(int32 bytes);
   void SubstractStorageSize(int32 bytes);