Rolling forward https://codereview.chromium.org/1155683008/ which was

third_party/polymer/v0_8/components-chromium/paper-dialog-scrollable/paper-dialog-scrollable-extracted.js

-
-
-(function() {
-
-  Polymer({
-
-    is: 'paper-dialog-scrollable',
-
-    properties: {
-
-      /**
-       * The dialog element that implements `Polymer.PaperDialogBehavior` containing this element.
-       */
-      dialogElement: {
-        type: Object,
-        value: function() {
-          return this.parentNode;
-        }
-      }
-
-    },
-
-    listeners: {
-      'scrollable.scroll': '_onScroll',
-      'iron-resize': '_onIronResize'
-    },
-
-    /**
-     * Returns the scrolling element.
-     */
-    get scrollTarget() {
-      return this.$.scrollable;
-    },
-
-    attached: function() {
-      this.classList.add('no-padding');
-      // Set itself to the overlay sizing target
-      this.dialogElement.sizingTarget = this.scrollTarget;
-      // If the host is sized, fit the scrollable area to the container. Otherwise let it be
-      // its natural size.
-      requestAnimationFrame(function() {
-        if (this.offsetHeight > 0) {
-          this.$.scrollable.classList.add('fit');
-        }
-        this._scroll();
-      }.bind(this));
-    },
-
-    _scroll: function() {
-      this.toggleClass('is-scrolled', this.scrollTarget.scrollTop > 0);
-      this.toggleClass('can-scroll', this.scrollTarget.offsetHeight < this.scrollTarget.scrollHeight);
-      this.toggleClass('scrolled-to-bottom',
-        this.scrollTarget.scrollTop + this.scrollTarget.offsetHeight >= this.scrollTarget.scrollHeight);
-    },
-
-    _onScroll: function() {
-      this._scroll();
-    }
-
-  })
-
-})();
-