| Index: samples/survey/web/elements/question/question_element.dart
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| diff --git a/samples/survey/web/elements/question/question_element.dart b/samples/survey/web/elements/question/question_element.dart
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| index 2023a9ec80a6a4bc6ad3c6ce00ea940957e13169..ccc07bee870d454969501b70f92f853df70509ed 100644
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| --- a/samples/survey/web/elements/question/question_element.dart
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| +++ b/samples/survey/web/elements/question/question_element.dart
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| @@ -14,7 +14,7 @@ import 'package:survey/models.dart';
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|   *  provide answer options to the user, and pick the widget that the user sees.
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|   */
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|  @CustomTag('question-element')
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| -class QuestionElement extends PolymerElement with ObservableMixin {
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| +class QuestionElement extends PolymerElement with Observable {
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|    static const String TEXTFIELD_OPT = 'Use a text field';
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|    static const String ONE_FROM_MANY_OPT = 'Select one from many options';
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|    static const String MANY_FROM_MANY_OPT = 'Select many from many options';
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| 
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