Import Polymer 0.8 and several key elements.

third_party/polymer/v0_8/components/iron-selector/iron-selection.html

Index: third_party/polymer/v0_8/components/iron-selector/iron-selection.html
diff --git a/third_party/polymer/v0_8/components/iron-selector/iron-selection.html b/third_party/polymer/v0_8/components/iron-selector/iron-selection.html
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+
+<!--
+Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+
+<link rel="import" href="../polymer/polymer.html">
+
+<script>
+
+  Polymer.IronSelection = function(selectCallback) {
+    this.selection = [];
+    this.selectCallback = selectCallback;
+  };
+
+  Polymer.IronSelection.prototype = {
+
+    /**
+     * Retrieves the selected item(s).
+     *
+     * @method get
+     * @returns Returns the selected item(s). If the multi property is true,
+     * `get` will return an array, otherwise it will return
+     * the selected item or undefined if there is no selection.
+     */
+    get: function() {
+      return this.multi ? this.selection : this.selection[0];
+    },
+
+    /**
+     * Clears all the selection except the ones indicated.
+     *
+     * @method clear
+     * @param {Array} excludes items to be excluded.
+     */
+    clear: function(excludes) {
+      this.selection.slice().forEach(function(item) {
+        if (!excludes || excludes.indexOf(item) < 0) {
+          this.setItemSelected(item, false);
+        }
+      }, this);
+    },
+
+    /**
+     * Indicates if a given item is selected.
+     *
+     * @method isSelected
+     * @param {any} item The item whose selection state should be checked.
+     * @returns Returns true if `item` is selected.
+     */
+    isSelected: function(item) {
+      return this.selection.indexOf(item) >= 0;
+    },
+
+    /**
+     * Sets the selection state for a given item to either selected or deselected.
+     *
+     * @method setItemSelected
+     * @param {any} item The item to select.
+     * @param {Boolean} isSelected True for selected, false for deselected.
+     */
+    setItemSelected: function(item, isSelected) {
+      if (item != null) {
+        if (isSelected) {
+          this.selection.push(item);
+        } else {
+          var i = this.selection.indexOf(item);
+          if (i >= 0) {
+            this.selection.splice(i, 1);
+          }
+        }
+        if (this.selectCallback) {
+          this.selectCallback(item, isSelected);
+        }
+      }
+    },
+
+    /**
+     * Sets the selection state for a given item. If the `multi` property
+     * is true, then the selected state of `item` will be toggled; otherwise
+     * the `item` will be selected.
+     *
+     * @method select
+     * @param {any} item The item to select.
+     */
+    select: function(item) {
+      if (this.multi) {
+        this.toggle(item);
+      } else if (this.get() !== item) {
+        this.setItemSelected(this.get(), false);
+        this.setItemSelected(item, true);
+      }
+    },
+
+    /**
+     * Toggles the selection state for `item`.
+     *
+     * @method toggle
+     * @param {any} item The item to toggle.
+     */
+    toggle: function(item) {
+      this.setItemSelected(item, !this.isSelected(item));
+    }
+
+  };
+
+</script>