Ensure properties override attributes at upgrade time. Fixes #3779.

src/lib/template/dom-bind.html

@@ -71,9 +71,9 @@
       Polymer.RenderStatus.whenReady(function() {
         if (document.readyState == 'loading') {
           document.addEventListener('DOMContentLoaded', function() {
-            self._markImportsReady(); 
+            self._markImportsReady();
           });
-        } else {  
+        } else {
           self._markImportsReady();
         }
       });
@@ -123,6 +123,11 @@
       }
     },
 
+    _configureInstanceProperties: function() {
+      // We use the _prepConfigure code below to read instance values before
+      // creating instance accessors, rather than the standard method here
+    },
+
     _prepConfigure: function() {
       var config = {};
       for (var prop in this._propertyEffects) {

src/standard/configure.html

@@ -92,6 +92,8 @@
       this._configureAnnotationReferences();
       // save copy of configuration that came from above
       this._aboveConfig = this.mixin({}, this._config);
+      // save instance properties that may have been bound prior to upgrade
+      this._configureInstanceProperties(this._aboveConfig);
       // get individual default values from property configs
       var config = {};
       // mixed-in behaviors
@@ -113,18 +115,23 @@
       }
     },
 
-    _configureProperties: function(properties, config) {
-      for (var i in properties) {
-        var c = properties[i];
+    _configureInstanceProperties: function(config) {
+      for (var i in this._propertyEffects) {
         // Allow properties set before upgrade on the instance
         // to override default values. This allows late upgrade + an early set
         // to not b0rk accessors on the prototype.
         // Perf testing has shown `hasOwnProperty` to be ok here.
-        if (!usePolyfillProto && this.hasOwnProperty(i) &&
-            this._propertyEffects && this._propertyEffects[i]) {
+        if (!usePolyfillProto && this.hasOwnProperty(i)) {
           config[i] = this[i];
           delete this[i];
-        } else if (c.value !== undefined) {
+        }
+      }
+    },
+
+    _configureProperties: function(properties, config) {
+      for (var i in properties) {
+        var c = properties[i];
+        if (c.value !== undefined) {
           var value = c.value;
           if (typeof value == 'function') {
             // pass existing config values (this._config) to value function