Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

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 45ce6ac62228aad5ab59a2e4aa731326563f2121..0e095430cf9d67fe55c53ae4576937a5a93674f4 100644
--- a/net/disk_cache/blockfile/backend_impl_v3.h
+++ b/net/disk_cache/blockfile/backend_impl_v3.h
@@ -188,6 +188,10 @@ class NET_EXPORT_PRIVATE BackendImplV3 : public Backend {
                          const CompletionCallback& callback) override;
   int DoomEntriesSince(base::Time initial_time,
                        const CompletionCallback& callback) override;
+  int CalculateSizeOfEntriesBetween(
+      base::Time initial_time,
+      base::Time end_time,
+      const CompletionCallback& callback) override;
   scoped_ptr<Iterator> CreateIterator() override;
   void GetStats(StatsItems* stats) override;
   void OnExternalCacheHit(const std::string& key) override;