Import Polymer 0.8 and several key elements.

third_party/polymer/v0_8/components/polymer/src/lib/array-observe.html

Index: third_party/polymer/v0_8/components/polymer/src/lib/array-observe.html
diff --git a/third_party/polymer/v0_8/components/polymer/src/lib/array-observe.html b/third_party/polymer/v0_8/components/polymer/src/lib/array-observe.html
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index 0000000000000000000000000000000000000000..998f59fc16a52b10db30cf5aef849529922e6629
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+<!--
+@license
+Copyright (c) 2014 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="debounce.html">
+
+<script>
+
+(function() {
+
+  var callbacks = new WeakMap();
+  
+  function observe(array, cb) {
+    if (Array.observe) {
+      var ncb = function(changes) {
+        changes = changes.filter(function(o) { return o.type == 'splice'; });
+        if (changes.length) {
+          cb(changes);
+        }
+      };
+      callbacks.set(cb, ncb);
+      Array.observe(array, ncb);
+    } else {
+      if (!array.__polymerObservable) {
+        makeObservable(array);
+      }
+      callbacks.get(array).push(cb);
+    }
+  }
+
+  function unobserve(array, cb) {
+    if (Array.observe) {
+      var ncb = callbacks.get(cb);
+      callbacks.delete(cb);
+      Array.unobserve(array, ncb);
+    } else {
+      var cbs = callbacks.get(array);
+      var idx = cbs.indexOf(cb);
+      if (idx >= 0) {
+        cbs.splice(idx, 1);
+      }
+    }
+  }
+
+  function makeObservable(array) {
+    var splices = [];
+    var debounce;
+    var orig = {
+      push: array.push,
+      pop: array.pop,
+      splice: array.splice,
+      shift: array.shift,
+      unshift: array.unshift,
+      sort: array.sort
+    };
+    var addSplice = function(index, added, removed) {
+      splices.push({
+        index: index,
+        addedCount: added,
+        removed: removed,
+        object: array,
+        type: 'splice'
+      });
+    };
+    callbacks.set(array, []);
+    array.push = function() {
+      debounce = Polymer.Debounce(debounce, fin);
+      addSplice(array.length, 1, []);
+      return orig.push.apply(this, arguments);
+    };
+    array.pop = function() {
+      debounce = Polymer.Debounce(debounce, fin);
+      addSplice(array.length - 1, 0, array.slice(-1));
+      return orig.pop.apply(this, arguments);
+    };
+    array.splice = function(start, deleteCount) {
+      debounce = Polymer.Debounce(debounce, fin);
+      addSplice(start, arguments.length - 2, array.slice(start, start + deleteCount));
+      return orig.splice.apply(this, arguments);
+    };
+    array.shift = function() {
+      debounce = Polymer.Debounce(debounce, fin);
+      addSplice(0, 0, [array[0]]);
+      return orig.shift.apply(this, arguments);
+    };
+    array.unshift = function() {
+      debounce = Polymer.Debounce(debounce, fin);
+      addSplice(0, 1, []);
+      return orig.unshift.apply(this, arguments);
+    };
+    array.sort = function() {
+      debounce = Polymer.Debounce(debounce, fin);
+      console.warn('[ArrayObserve]: sort not observable');
+      return orig.sort.apply(this, arguments);
+    };
+    var fin = function() {
+      var cbs = callbacks.get(array);
+      for (var i=0; i<cbs.length; i++) {
+        cbs[i](splices);
+      }
+      splices = [];
+    };
+    array.__polymerObservable = true;
+  }
+
+  Polymer.ArrayObserve = {
+    observe: observe,
+    unobserve: unobserve
+  };
+  
+})();
+
+</script>