[analyzer] Property defined in the mixin constructor does not have description and type definition

[web-padawan]

In some of the components and mixins we have property definitions like this:

    constructor() {
      super();
      /**
       * Submittable string value. The default value is the trimmed text content of the element.
       * @type {string}
       */
      this.value;
    }
    get value() {
      return this._value !== undefined ? this._value : this.textContent.trim();
    }
    set value(value) {
      this._value = value;
    }

With latest polymer-cli it only works for elements, but not for mixins.

Before

"name": "value",
"type": "string",
"description": "Submittable string value. The default value is the trimmed text content of the element.",

Permalink:
https://github.com/vaadin/vaadin-item/blob/699c0c8ebb89f6004aa6de5a011b0a9294a23939/analysis.json#L26

After

"name": "value",
"type": "?",
"description": "",

Permalink:
https://github.com/vaadin/vaadin-item/blob/bd28f0b29b3fbd977fee1c0303abde4ef4aa1d65/analysis.json#L26

Note: the same JSDoc annotation in vaadin-checkbox element (not mixin) working fine with the latest analyzer in polymer-cli 1.7.7: https://github.com/vaadin/vaadin-checkbox/blob/e9af82ba9b6017af03d214d3a9286018f4beab5d/src/vaadin-checkbox.html#L158

[43081j]

FYI its because we overwrite the property when scanning the accessor.

Guess we should be merging instead of overwriting on second scan.

Happy to fix it once i figure how we should handle that.