Fixes #4601. Client elements can be readied that have already enabled…

… properties. This can happen when templatize is used to create instances with no properties. In this case, in order for properties to flush properly to clients, clients must be flushed.

lib/mixins/property-effects.html

@@ -1466,6 +1466,8 @@
             let client = clients[i];
             if (!client.__dataEnabled) {
               client._enableProperties();
+            } else {
+              client._flushProperties();
             }
           }
         }

test/unit/templatize.html

@@ -181,6 +181,20 @@
       assert.isUndefined(childB.computedFromLiteral);
     });
 
+    test('templatize with no props, instance manually flushes', function() {
+      let templatizeA = host.shadowRoot.querySelector('[id=templatizeA]');
+      templatizeA.go(false);
+      let childA = host.shadowRoot.querySelector('#childA');
+      assert.ok(childA);
+      sinon.spy(childA, 'objChanged');
+      assert.isUndefined(childA.obj);
+      let o = {foo: true};
+      templatizeA.instance._setPendingProperty('obj', o);
+      templatizeA.instance._flushProperties();
+      assert.equal(childA.obj, o);
+      assert.isTrue(childA.objChanged.calledOnce);
+    });
+
   });
 
   suite('templatizer behavior', function() {