[21:30:40.825] web-o-puzzle: An exception occurred.
NS_ERROR_FAILURE: Failure
Traceback (most recent call last):
  File "resource://gre/modules/commonjs/sdk/tabs/observer.js", line 49, in handleEvent
    this._emit(EVENTS[event.type], event.target, event);
  File "resource://gre/modules/commonjs/sdk/deprecated/events.js", line 123, in _emit
    return this._emitOnObject.apply(this, args);
  File "resource://gre/modules/commonjs/sdk/deprecated/events.js", line 153, in _emitOnObject
    listener.apply(targetObj, params);
  File "resource://gre/modules/commonjs/sdk/windows/tabs-firefox.js", line 120, in _onTabEvent
    this._emitEvent(type, wrappedTab);
  File "resource://gre/modules/commonjs/sdk/windows/tabs-firefox.js", line 130, in _emitEvent
    this._tabs._emit.apply(this._tabs, args);
  File "resource://gre/modules/commonjs/sdk/deprecated/events.js", line 123, in _emit
    return this._emitOnObject.apply(this, args);
  File "resource://gre/modules/commonjs/sdk/deprecated/events.js", line 153, in _emitOnObject
    listener.apply(targetObj, params);
  File "resource://gre/modules/commonjs/sdk/tabs/tab-firefox.js", line 129, in _onEvent
    this._emit(type, tab);
  File "resource://gre/modules/commonjs/sdk/deprecated/events.js", line 123, in _emit
    return this._emitOnObject.apply(this, args);
  File "resource://gre/modules/commonjs/sdk/deprecated/events.js", line 153, in _emitOnObject
    listener.apply(targetObj, params);
  File "resource://jid0-9neth0itobkezwy0uc8czjyqax4-at-jetpack/web-o-puzzle/lib/game_tab.js", line 11, in exports.open/<.onOpen
    contentScriptOptions: {dataurl: foxyshot.capturePage()}
  File "resource://jid0-9neth0itobkezwy0uc8czjyqax4-at-jetpack/web-o-puzzle/lib/foxyshot.js", line 24, in exports.capturePage
    (shot(width, height, function (context) {
  File "resource://jid0-9neth0itobkezwy0uc8czjyqax4-at-jetpack/web-o-puzzle/lib/foxyshot.js", line 8, in shot
    callback(context);
  File "resource://jid0-9neth0itobkezwy0uc8czjyqax4-at-jetpack/web-o-puzzle/lib/foxyshot.js", line 25, in exports.capturePage/<
    context.drawWindow(documentWindow, x, y, width, height, 'rgb(0, 0, 0)');