Implement autoplay gesture override experiment.

public/web/WebSettings.h

 /*
  * Copyright (C) 2009 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 259 matching lines @@
     virtual void setViewportMetaEnabled(bool) = 0;
     virtual void setViewportMetaLayoutSizeQuirk(bool) = 0;
     virtual void setViewportMetaMergeContentQuirk(bool) = 0;
     virtual void setViewportMetaNonUserScalableQuirk(bool) = 0;
     virtual void setViewportMetaZeroValuesQuirk(bool) = 0;
     virtual void setWebAudioEnabled(bool) = 0;
     virtual void setWebGLErrorsToConsoleEnabled(bool) = 0;
     virtual void setWebSecurityEnabled(bool) = 0;
     virtual void setWideViewportQuirkEnabled(bool) = 0;
     virtual void setXSSAuditorEnabled(bool) = 0;
+    virtual void setAutoplayExperimentMode(const WebString&) = 0;

[dglazkov, 2015/08/06 20:55:23]

Let's not use a String here. Take a look at how TextTrackKindUserPreference is
used for an alternative.

[liberato (no reviews please), 2015/09/01 06:54:19]

I tried several approaches to make Settings.in take an enum, and they all have
some significant drawbacks.  TextTrackKindUserPreference is accessed from
outside blink as an enum, which isn't what i want.  i'd like to send in
human-readable strings, so that (e.g.) the finch experiment config doesn't have
experiment mode "3", but rather "enabled-ifviewport".  so, i need a string
parser somewhere, both for the tests and for outside WebKit.

however, i could find no single place to put the parser such that it can be
accessed both from outside blink and from the layout tests.  InternalSettings is
where TextTrack* adds a parser for the tests, but that's not going to help blink
consumers.  if there is some way have one parser implementation that both
about::flags and that blink layout tests could use, then that would make it all
work out.

so, after spending a fair bit of time trying to make it better, i moved back to
strings in the settings.  i did encapsulate the parsing in a separate helper
class, just to clean it up a little.

if i've missed some approach that avoids these issues, please let me know.

 
 protected:
     ~WebSettings() { }
 };
 
 } // namespace blink
 
 #endif