Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

net/disk_cache/blockfile/backend_impl.cc

Index: net/disk_cache/blockfile/backend_impl.cc
diff --git a/net/disk_cache/blockfile/backend_impl.cc b/net/disk_cache/blockfile/backend_impl.cc
index 82a58b36b6d1f37c45e5b326554a835ea50c7b64..97f35208a8a2c1ec50ac2846501a65a0d821ed29 100644
--- a/net/disk_cache/blockfile/backend_impl.cc
+++ b/net/disk_cache/blockfile/backend_impl.cc
@@ -410,6 +410,14 @@ int BackendImpl::SyncDoomEntriesBetween(const base::Time initial_time,
   return net::OK;
 }
 
+int BackendImpl::SyncCalculateSizeOfAllEntries() {
+  DCHECK_NE(net::APP_CACHE, cache_type_);
+  if (disabled_)
+    return net::ERR_FAILED;
+
+  return data_->header.num_bytes;
+}
+
 // We use OpenNextEntryImpl to retrieve elements from the cache, until we get
 // entries that are too old.
 int BackendImpl::SyncDoomEntriesSince(const base::Time initial_time) {
@@ -1254,6 +1262,12 @@ int BackendImpl::DoomEntriesSince(const base::Time initial_time,
   return net::ERR_IO_PENDING;
 }
 
+int BackendImpl::CalculateSizeOfAllEntries(const CompletionCallback& callback) {
+  DCHECK(!callback.is_null());
+  background_queue_.CalculateSizeOfAllEntries(callback);
+  return net::ERR_IO_PENDING;
+}
+
 class BackendImpl::IteratorImpl : public Backend::Iterator {
  public:
   explicit IteratorImpl(base::WeakPtr<InFlightBackendIO> background_queue)