Add Resource Handler for creating Streams to forward to extensions

content/browser/streams/stream_write_observer.h

Index: content/browser/streams/stream_write_observer.h
diff --git a/content/browser/streams/stream_write_observer.h b/content/browser/streams/stream_write_observer.h
index 31d84cdef56a615216426f99b1311c4a1ea878e9..deab7ad009ef2cd7e00f155682b80d2d604192a0 100644
--- a/content/browser/streams/stream_write_observer.h
+++ b/content/browser/streams/stream_write_observer.h
@@ -15,6 +15,9 @@ class StreamWriteObserver {
   // resume writing.
   virtual void OnSpaceAvailable(Stream* stream) = 0;
 
+  // Sent when the stream is closed, and the writer should stop sending data.
+  virtual void OnClose(Stream* stream) = 0;
+
  protected:
   virtual ~StreamWriteObserver() {}
 };