Remove support for a URLRequest having a NULL Delegate.

storage/browser/fileapi/file_writer_delegate.cc

Index: storage/browser/fileapi/file_writer_delegate.cc
diff --git a/storage/browser/fileapi/file_writer_delegate.cc b/storage/browser/fileapi/file_writer_delegate.cc
index ab264d3b517fc1919a362e6750557c3b52dde6ec..469a7023f7e1dcc02b293ccec796d6e49be4cd1a 100644
--- a/storage/browser/fileapi/file_writer_delegate.cc
+++ b/storage/browser/fileapi/file_writer_delegate.cc
@@ -45,9 +45,8 @@ void FileWriterDelegate::Start(scoped_ptr<net::URLRequest> request,
 
 void FileWriterDelegate::Cancel() {
   if (request_) {
-    // This halts any callbacks on this delegate.
-    request_->set_delegate(NULL);
-    request_->Cancel();
+    // Destroy the request to prevent it from invoking any callbacks.
+    request_.reset();
   }
 
   const int status = file_stream_writer_->Cancel(
@@ -173,8 +172,8 @@ FileWriterDelegate::GetCompletionStatusOnError() const {
 
 void FileWriterDelegate::OnError(base::File::Error error) {
   if (request_) {
-    request_->set_delegate(NULL);
-    request_->Cancel();
+    // Destroy the request to prevent it from invoking any callbacks.
+    request_.reset();
   }
 
   if (writing_started_)