Add flag "distillability-dev" for distillability development

components/dom_distiller/core/dom_distiller_switches.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/dom_distiller/core/dom_distiller_switches.h"
 
 namespace switches {
 
 const char kEnableDomDistiller[] = "enable-dom-distiller";
+const char kDistillabilityDev[] = "distillability-dev";
 const char kEnableSyncArticles[] = "enable-sync-articles";
 const char kReaderModeHeuristics[] = "reader-mode-heuristics";
 const char kReaderModeFeedback[] = "reader-mode-feedback";
 
 namespace reader_mode_heuristics {
 const char kAdaBoost[] = "adaboost";
 const char kOGArticle[] = "opengraph";
 const char kAlwaysTrue[] = "alwaystrue";
 const char kNone[] = "none";
 };
 
 namespace reader_mode_feedback {
 const char kOn[] = "on";
 const char kOff[] = "off";
 };
 
 }  // namespace switches