DevTools: promisify ContentProvider.requestContent and all its clients.

third_party/WebKit/Source/devtools/front_end/network/NetworkItemView.js

 /*
  * Copyright (C) 2010 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 134 matching lines @@
         /**
          * @param {?string} content
          * @this {WebInspector.RequestContentView}
          */
         function callback(content)
         {
             this._innerViewShowRequested = false;
             this.contentLoaded();
         }
 
-        this.request.requestContent(callback.bind(this));
+        this.request.requestContent().then(callback.bind(this));
     },
 
     contentLoaded: function()
     {
         // Should be implemented by subclasses.
     },
 
     __proto__: WebInspector.RequestView.prototype
 }