Apply to _marshalArgs.

src/lib/bind/effects.html

@@ -8,6 +8,8 @@
 subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 -->
 <link rel="import" href="../case-map.html">
+<link rel="import" href="../path.html">
+
 <script>
 
   Polymer.Base.extend(Polymer.Bind, {
@@ -144,8 +146,7 @@
           // caused the observer to run matches this arg. Note that this holds
           // also true when `path === name`. We can skip this check b/c then
           // `name` and `v` already have the values we want.
-          // Read the following as: `head(path) === name`.
-          var matches = path.indexOf(name + '.') === 0;
+          var matches = Polymer.Path.isAncestor(path, name);
           values[i] = {
             path: matches ? path : name,
             value: matches ? value : v,