Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

net/disk_cache/blockfile/entry_impl.h

Index: net/disk_cache/blockfile/entry_impl.h
diff --git a/net/disk_cache/blockfile/entry_impl.h b/net/disk_cache/blockfile/entry_impl.h
index aafb59b66a295d0df8f1b417d85430ee0ef5bf28..0e8eb3852d2313d7bf5da1e8cc0411d92cd5f7ec 100644
--- a/net/disk_cache/blockfile/entry_impl.h
+++ b/net/disk_cache/blockfile/entry_impl.h
@@ -146,6 +146,9 @@ class NET_EXPORT_PRIVATE EntryImpl
   // Returns the number of blocks needed to store an EntryStore.
   static int NumBlocksForEntry(int key_size);
 
+  // The total size of this entry; sum of |GetDataSize| for all streams.
+  int GetEntrySize() const;
+
   // Entry interface.
   void Doom() override;
   void Close() override;