Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

net/disk_cache/blockfile/backend_impl.h

Index: net/disk_cache/blockfile/backend_impl.h
diff --git a/net/disk_cache/blockfile/backend_impl.h b/net/disk_cache/blockfile/backend_impl.h
index d3a81ac2d1ba6767685d9832187df6218eb76e3e..4bf7e0580f6564f0d26e9c94013386f9694482bf 100644
--- a/net/disk_cache/blockfile/backend_impl.h
+++ b/net/disk_cache/blockfile/backend_impl.h
@@ -74,6 +74,8 @@ class NET_EXPORT_PRIVATE BackendImpl : public Backend {
   int SyncDoomEntriesBetween(base::Time initial_time,
                              base::Time end_time);
   int SyncDoomEntriesSince(base::Time initial_time);
+  int SyncCalculateSizeOfEntriesBetween(base::Time initial_time,
+                                        base::Time end_time);
   int SyncOpenNextEntry(Rankings::Iterator* iterator, Entry** next_entry);
   void SyncEndEnumeration(scoped_ptr<Rankings::Iterator> iterator);
   void SyncOnExternalCacheHit(const std::string& key);
@@ -275,6 +277,10 @@ class NET_EXPORT_PRIVATE BackendImpl : 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;
   // NOTE: The blockfile Backend::Iterator::OpenNextEntry method does not modify
   // the last_used field of the entry, and therefore it does not impact the
   // eviction ranking of the entry. However, an enumeration will go through all