Roll Polymer elements

third_party/polymer/v1_0/components-chromium/app-layout/app-scrollpos-control/app-scrollpos-control-extracted.js

+Polymer({
+      is: 'app-scrollpos-control',
+
+      properties: {
+        /**
+         * The selected page.
+         */
+        selected: {
+          type: String,
+          observer: '_selectedChanged'
+        },
+
+        /**
+         * Reset the scroll position to 0.
+         */
+        reset: {
+          type: Boolean,
+          value: false
+        }
+      },
+
+      observers: [
+        '_updateScrollPos(selected, reset)'
+      ],
+
+      created: function() {
+        this._scrollposMap = {};
+      },
+
+      _selectedChanged: function(selected, old) {
+        if (old != null) {
+          this._scrollposMap[old] = {x: window.pageXOffset, y: window.pageYOffset};
+        }
+      },
+
+      _updateScrollPos: function(selected, reset) {
+        this.debounce('_updateScrollPos', function() {
+          var pos = this._scrollposMap[this.selected];
+          if (pos != null && !this.reset) {
+            this._scrollTo(pos.x, pos.y);
+          } else {
+            this._scrollTo(0, 0);
+          }
+        });
+      },
+
+      _scrollTo: function(x, y) {
+        Polymer.AppLayout.scroll({
+          left: x,
+          top: y,
+          behavior: 'silent'
+        });
+      }
+    });