Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/loader/redirect_to_file_resource_handler.cc

Index: content/browser/loader/redirect_to_file_resource_handler.cc
diff --git a/content/browser/loader/redirect_to_file_resource_handler.cc b/content/browser/loader/redirect_to_file_resource_handler.cc
index b9784b0676e5317301edd21032dbba323dc3d94d..3bddfd75d301dfebfb755ebc993036685ed506f7 100644
--- a/content/browser/loader/redirect_to_file_resource_handler.cc
+++ b/content/browser/loader/redirect_to_file_resource_handler.cc
@@ -185,9 +185,10 @@ void RedirectToFileResourceHandler::OnWillStart(
   }
 }
 
-bool RedirectToFileResourceHandler::OnWillRead(
+void RedirectToFileResourceHandler::OnWillRead(
     scoped_refptr<net::IOBuffer>* buf,
-    int* buf_size) {
+    int* buf_size,
+    std::unique_ptr<ResourceController> controller) {
   if (buf_->capacity() < next_buffer_size_)
     buf_->SetCapacity(next_buffer_size_);
 
@@ -198,7 +199,7 @@ bool RedirectToFileResourceHandler::OnWillRead(
   *buf_size = buf_->RemainingCapacity();
 
   buf_write_pending_ = true;
-  return true;
+  controller->Resume();
 }
 
 void RedirectToFileResourceHandler::OnReadCompleted(