extensions/amp-position-observer/0.1/amp-position-observer.js
/**
   * Margins can be of `vh` unit which means they may need to be recalculated
   * when viewport height changes.
   * @private
   */
Margins can be of `vh` unit which means they may need to be recalculated
when viewport height changes.
@private
Margins can be of ` vh ` unit which means they may need to be recalculated when viewport height changes . @private
recalculateMargins_() {
    dev().assert(this.viewportRect_);
    dev().assert(this.bottomMarginExpr_);
    dev().assert(this.topMarginExpr_);
    this.resolvedTopMargin_ =
        this.validateAndResolveMargin_(this.topMarginExpr_);
    this.resolvedBottomMargin_ =
        this.validateAndResolveMargin_(this.bottomMarginExpr_);
  }
recalculateMargins_ ( ) { dev ( ) . assert ( this . viewportRect_ ) ; dev ( ) . assert ( this . bottomMarginExpr_ ) ; dev ( ) . assert ( this . topMarginExpr_ ) ; this . resolvedTopMargin_ = this . validateAndResolveMargin_ ( this . topMarginExpr_ ) ; this . resolvedBottomMargin_ = this . validateAndResolveMargin_ ( this . bottomMarginExpr_ ) ; }
Margins can be of `vh` unit which means they may need to be recalculated
 when viewport height changes.
Margins can be of ` vh ` unit which means they may need to be recalculated when viewport height changes .