Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/loader/layered_resource_handler.cc

Index: content/browser/loader/layered_resource_handler.cc
diff --git a/content/browser/loader/layered_resource_handler.cc b/content/browser/loader/layered_resource_handler.cc
index d1cf3a4933566bcfa433095ee5a21d8ec94768db..91d1787499917d7c1eff38a4f60a7acbb0dd7460 100644
--- a/content/browser/loader/layered_resource_handler.cc
+++ b/content/browser/loader/layered_resource_handler.cc
@@ -47,10 +47,12 @@ void LayeredResourceHandler::OnWillStart(
   next_handler_->OnWillStart(url, std::move(controller));
 }
 
-bool LayeredResourceHandler::OnWillRead(scoped_refptr<net::IOBuffer>* buf,
-                                        int* buf_size) {
+void LayeredResourceHandler::OnWillRead(
+    scoped_refptr<net::IOBuffer>* buf,
+    int* buf_size,
+    std::unique_ptr<ResourceController> controller) {
   DCHECK(next_handler_.get());
-  return next_handler_->OnWillRead(buf, buf_size);
+  return next_handler_->OnWillRead(buf, buf_size, std::move(controller));
 }
 
 void LayeredResourceHandler::OnReadCompleted(