Removal of rel=preload link elements should stop the download.

third_party/WebKit/Source/core/loader/LinkLoader.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 303 matching lines @@
 }
 
 void LinkLoader::released()
 {
     // Only prerenders need treatment here; other links either use the Resource interface, or are notionally
     // atomic (dns prefetch).
     if (m_prerender) {
         m_prerender->cancel();
         m_prerender.clear();
     }
+    if (m_linkPreloadResourceClient)
+        m_linkPreloadResourceClient->cancel();

[Nate Chapin, 2016/01/21 19:03:50]

Can you get the correct behavior here by just calling
m_linkPreloadResourceClient.clear()?

[Yoav Weiss, 2016/01/21 21:51:20]

Didn't really work, but clearResource inside the linkPreloadResourceClient did.

 }
 
 DEFINE_TRACE(LinkLoader)
 {
     visitor->trace(m_prerender);
     visitor->trace(m_linkPreloadResourceClient);
     ResourceOwner<Resource, ResourceClient>::trace(visitor);
 }
 
 }