Add FileReader interface and implement FileSystemFileReader

webkit/blob/blob_url_request_job.cc

Index: webkit/blob/blob_url_request_job.cc
diff --git a/webkit/blob/blob_url_request_job.cc b/webkit/blob/blob_url_request_job.cc
index 147753a09b89084367b3aff86a13ba279722b1dc..31045ff60c5fe2fb2d6dc1caa4e4b53671324144 100644
--- a/webkit/blob/blob_url_request_job.cc
+++ b/webkit/blob/blob_url_request_job.cc
@@ -218,7 +218,7 @@ void BlobURLRequestJob::DidCountSize(int error) {
   NotifySuccess();
 }
 
-void BlobURLRequestJob::DidGetFileItemLength(size_t index, int result) {
+void BlobURLRequestJob::DidGetFileItemLength(size_t index, int64 result) {
   // Do nothing if we have encountered an error.
   if (error_)
     return;
@@ -239,7 +239,7 @@ void BlobURLRequestJob::DidGetFileItemLength(size_t index, int result) {
   // in the real time.
   int64 item_length = static_cast<int64>(item.length);
   if (item_length == -1)
-    item_length = result;
+    item_length = result - item.offset;
 
   // Cache the size and add it to the total size.
   DCHECK_LT(index, item_length_list_.size());