Remove unnecessary setting of _template.

lib/legacy/class.html

@@ -493,15 +493,6 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       klass = GenerateClassFromInfo(info, klass, info.behaviors);
       // decorate klass with registration info
       klass.is = info.is;
-      // To match 1.x behavior, `_template` supplied on a behavior should take
-      // precedence over dom-module lookup for `is`; this also prevents
-      // dom-module injection under strictTemplatePolicy for an element that
-      // would normally get its template from a behavior.
-      // TODO(sorvell): Remove once "flattened behaviors" lands, since both
-      // `_template` and `is` will be on the same class after that change
-      if (klass.prototype._template !== undefined) {
-        klass.prototype._template = klass.prototype._template;
-      }
       return klass;
     };