Lower priority of async scripts

Source/core/fetch/FetchRequest.h

 /*
  * Copyright (C) 2012 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 38 matching lines @@
     ResourceRequest& mutableResourceRequest() { return m_resourceRequest; }
     const ResourceRequest& resourceRequest() const { return m_resourceRequest; }
     const KURL& url() const { return m_resourceRequest.url(); }
     const String& charset() const { return m_charset; }
     void setCharset(const String& charset) { m_charset = charset; }
     const ResourceLoaderOptions& options() const { return m_options; }
     void setOptions(const ResourceLoaderOptions& options) { m_options = options; }
     ResourceLoadPriority priority() const { return m_priority; }
     bool forPreload() const { return m_forPreload; }
     void setForPreload(bool forPreload) { m_forPreload = forPreload; }
+    bool execAsync() const { return m_execAsync; }
+    void setExecAsync(bool execAsync) { m_execAsync = execAsync; }
     DeferOption defer() const { return m_defer; }
     void setDefer(DeferOption defer) { m_defer = defer; }
     void setContentSecurityCheck(ContentSecurityPolicyCheck contentSecurityPolicyOption) { m_options.contentSecurityPolicyOption = contentSecurityPolicyOption; }
     void setCrossOriginAccessControl(SecurityOrigin*, StoredCredentials, CredentialRequest);
     void setCrossOriginAccessControl(SecurityOrigin*, StoredCredentials);
     void setCrossOriginAccessControl(SecurityOrigin*, const AtomicString& crossOriginMode);
     OriginRestriction originRestriction() const { return m_originRestriction; }
     void setOriginRestriction(OriginRestriction restriction) { m_originRestriction = restriction; }
 
 private:
     ResourceRequest m_resourceRequest;
     String m_charset;
     ResourceLoaderOptions m_options;
     ResourceLoadPriority m_priority;
     bool m_forPreload;
+    bool m_execAsync;

[eseidel, 2014/09/03 15:15:38]

Strange that this is different from DeferOption.

[Pat Meenan, 2014/09/03 16:16:17]

Looks like DeferOption is specific to images right now (if Chrome decides it
shouldn't load the image) and it completely blocks the fetch:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

I could expand the enum to include an indicator that it should still be loaded
but asynchronously which would eliminate the parallel execAsync plumbing.  I'm a
bit concerned that it might be confusing though since the current use of
DeferOption is to actually prevent the fetches.

     DeferOption m_defer;
     OriginRestriction m_originRestriction;
 };
 
 } // namespace blink
 
 #endif