Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

net/disk_cache/blockfile/backend_impl_v3.cc

Index: net/disk_cache/blockfile/backend_impl_v3.cc
diff --git a/net/disk_cache/blockfile/backend_impl_v3.cc b/net/disk_cache/blockfile/backend_impl_v3.cc
index fd572c3e226ae0954a1204eb6e4e978e48c0231d..fe944e8bf5c369091deea7490f39073533018f81 100644
--- a/net/disk_cache/blockfile/backend_impl_v3.cc
+++ b/net/disk_cache/blockfile/backend_impl_v3.cc
@@ -1508,6 +1508,10 @@ int BackendImplV3::DoomEntriesSince(base::Time initial_time,
   return net::ERR_FAILED;
 }
 
+int BackendImplV3::CalculateSizeOfAllEntries(
+    const CompletionCallback& callback) {
+  return net::ERR_FAILED;
+}
 
 class BackendImplV3::NotImplementedIterator : public Backend::Iterator {
  public: