Ensure fragments added via Polymer.dom always have elements removed, even when distribution does not select those elements.

src/lib/dom-api-shady.html

@@ -56,7 +56,8 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
           'of this node');
       }
       // remove node from its current position iff it's in a tree.
-      if (node.nodeType !== Node.DOCUMENT_FRAGMENT_NODE) {
+      var isFragment = node.nodeType === Node.DOCUMENT_FRAGMENT_NODE;
+      if (!isFragment) {
         var parent = TreeApi.Logical.getParentNode(node);
         // notify existing parent that this node is being removed.
         if (parent) {
@@ -81,6 +82,11 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
         } else {
           TreeApi.Composed.appendChild(container, node);
         }
+      // if a fragment provoked distribution, clean up it's actual dom.
+      } else if (isFragment) {
+        while (node.firstChild) {
+          node.removeChild(node.firstChild);
+        }
       }
       this.notifyObserver();
       return node;

test/unit/polymer-dom-content.html

@@ -1439,6 +1439,16 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       });
     });
 
+    test('adding a document fragment always clears nodes in the fragment', function() {
+      var x = document.createElement('x-dist-star');
+      var frag = document.createDocumentFragment();
+      frag.appendChild(document.createTextNode('hi'));
+      frag.appendChild(document.createElement('div'));
+      Polymer.dom(x).appendChild(frag);
+      Polymer.dom.flush();
+      assert.equal(frag.childNodes.length, 0);
+    });
+
   });