Allow MojoAsyncResourceHandler::OnWillRead to complete asyncronously

content/browser/loader/mojo_async_resource_handler.h

Index: content/browser/loader/mojo_async_resource_handler.h
diff --git a/content/browser/loader/mojo_async_resource_handler.h b/content/browser/loader/mojo_async_resource_handler.h
index b8cd1e57ec90cfe96e71e48d648daf255929e742..6ef4456eb450e3f636d060cc07b84d0dab70a2ef 100644
--- a/content/browser/loader/mojo_async_resource_handler.h
+++ b/content/browser/loader/mojo_async_resource_handler.h
@@ -132,11 +132,19 @@ class CONTENT_EXPORT MojoAsyncResourceHandler
   bool has_checked_for_sufficient_resources_ = false;
   bool sent_received_response_message_ = false;
   bool is_using_io_buffer_not_from_writer_ = false;
+  // True if OnWillRead was deferred, in order to wait to be able to allocate a
+  // buffer.
+  bool did_defer_on_will_read_ = false;
   bool did_defer_on_writing_ = false;
   bool did_defer_on_redirect_ = false;
   base::TimeTicks response_started_ticks_;
   int64_t reported_total_received_bytes_ = 0;
 
+  // Pointer to parent's information about the read buffer. Only non-null while
+  // OnWillRead is deferred.
+  scoped_refptr<net::IOBuffer>* parent_buffer_ = nullptr;
+  int* parent_buffer_size_ = nullptr;
+
   mojo::Watcher handle_watcher_;
   std::unique_ptr<mojom::URLLoader> url_loader_;
   mojom::URLLoaderClientPtr url_loader_client_;