Prevent URLFetcher::AppendChunkedData from dereferencing NULL pointers.

net/base/chunked_upload_data_stream.cc

Index: net/base/chunked_upload_data_stream.cc
diff --git a/net/base/chunked_upload_data_stream.cc b/net/base/chunked_upload_data_stream.cc
index 2b9c4807c7a25996726c6db3cfc87abbea7d2587..7ddd9418dbc331fe5c9891ee5521773d404df638 100644
--- a/net/base/chunked_upload_data_stream.cc
+++ b/net/base/chunked_upload_data_stream.cc
@@ -10,17 +10,37 @@
 
 namespace net {
 
+ChunkedUploadDataStream::Writer::~Writer() {}
+
+bool ChunkedUploadDataStream::Writer::AppendData(const char* data,
+                                                 int data_len,
+                                                 bool is_done) {
+  if (!upload_data_stream_)
+    return false;
+  upload_data_stream_->AppendData(data, data_len, is_done);
+  return true;
+}
+
+ChunkedUploadDataStream::Writer::Writer(
+    base::WeakPtr<ChunkedUploadDataStream> upload_data_stream)
+    : upload_data_stream_(upload_data_stream) {}
+
 ChunkedUploadDataStream::ChunkedUploadDataStream(int64_t identifier)
     : UploadDataStream(true, identifier),
       read_index_(0),
       read_offset_(0),
       all_data_appended_(false),
-      read_buffer_len_(0) {
-}
+      read_buffer_len_(0),
+      weak_factory_(this) {}
 
 ChunkedUploadDataStream::~ChunkedUploadDataStream() {
 }
 
+scoped_ptr<ChunkedUploadDataStream::Writer>
+ChunkedUploadDataStream::CreateWriter() {
+  return make_scoped_ptr(new Writer(weak_factory_.GetWeakPtr()));
+}
+
 void ChunkedUploadDataStream::AppendData(
     const char* data, int data_len, bool is_done) {
   DCHECK(!all_data_appended_);