Fix Resource Priorities and Scheduling (Blink Side)

Source/core/fetch/FetchContext.h

 /*
  * Copyright (C) 2013 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 90 matching lines @@
     virtual bool pageDismissalEventBeingDispatched() const { return false; }
     virtual bool updateTimingInfoForIFrameNavigation(ResourceTimingInfo*) { return false; }
     virtual void sendImagePing(const KURL&);
     virtual void addConsoleMessage(const String&) const;
     virtual SecurityOrigin* securityOrigin() const { return nullptr; }
     virtual void upgradeInsecureRequest(FetchRequest&);
     virtual void addClientHintsIfNecessary(FetchRequest&);
     virtual void addCSPHeaderIfNecessary(Resource::Type, FetchRequest&);
     virtual bool isLowPriorityIframe() const { return false; }
 
+    virtual bool fetchDeferLateScripts() const { return false; }
+    virtual bool fetchIncreaseFontPriority() const { return false; }
+    virtual bool fetchIncreaseAsyncScriptPriority() const { return false; }
+    virtual bool fetchIncreasePriorities() const { return false; }

[Nate Chapin, 2015/08/11 17:41:56]

This name is really vague. What priorities are being increased?

[Pat Meenan, 2015/08/11 18:50:10]

ResourceFetcher.cpp has a comment describing the full set of changes but there
are a bunch of them that all have to happen in concert (which is why they are
not individual toggles):

// Increases the priorities for CSS, Scripts, Fonts and Images all by one level
// and parser-blocking scripts and visible images by 2.
// This is used in conjunction with logic on the Chrome side to raise the
threshold
// of "layout-blocking" resources and provide a boost to resources that are
needed
// as soon as possible for something currently on the screen.

I can't think of a short but clear way to describe that but I'm happy to take
suggestions.  I could also include the comment here if that would help (or in
settings.in)

[Nate Chapin, 2015/08/12 21:13:47]

A comment in Settings.in is probably a good idea. That should be sufficient,
especially since this flag is presumably not going to be here too long?

[Pat Meenan, 2015/08/12 21:48:22]

Done.  The plan is to pull all of the experiment code out and settle on the new
priority values as soon as we get enough data back from the field trial (2-3
releases would be my guess before data from stable comes back).

+
 protected:
     FetchContext() { }
 };
 
 }
 
 #endif