Behavior property copying fixes

* ensure element has `is` on prototype early as this is sometimes checked in user code.
* ensure properties copied onto elements from info/behaviors are forced to configurable so they can be re-configured by later behaviors.
* add `_noAccessors` optimization for faster property copying

test/unit/behaviors.html

@@ -379,6 +379,20 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       behaviors: [window.BehaviorA]
     });
 
+    Polymer({
+      is: 'no-accessors-behavior',
+      behaviors: [{
+        _noAccessors: true,
+        properties: {
+          nug: String
+        },
+        foo: function() {},
+        bar: true
+      }],
+      _noAccessors: true,
+      zot: 'zot'
+    });
+
 </script>
 
   <test-fixture id="single">
@@ -447,6 +461,12 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
     </template>
   </test-fixture>
 
+  <test-fixture id="no-accessors-behavior">
+    <template>
+      <no-accessors-behavior></no-accessors-behavior>
+    </template>
+  </test-fixture>
+
 <script type="module">
 import { Polymer } from '../../polymer-legacy.js';
 
@@ -501,6 +521,15 @@ suite('single behavior element', function() {
     assert.notOk(el.listeners);
   });
 
+  test('properties on objects marked with `_noAccessors` are copied to class', function() {
+    const el = fixture('no-accessors-behavior');
+    assert.ok(el.foo);
+    assert.isTrue(el.bar);
+    assert.equal(el.zot, 'zot');
+    el.setAttribute('nug', 'nug');
+    assert.equal(el.nug, 'nug');
+  });
+
 });
 
 suite('behavior.registered', function() {