Force all expressions to reset deps on changes.

This is required with the current approach because path objects may become reachable.

See: #21

R=arv
BUG=

Review URL: https://codereview.appspot.com/53530043

src/polymer-expressions.js

@@ -389,13 +389,16 @@
       var self = this;
 
       function valueFn() {
-        if (self.dynamicDeps)
+        // TODO(rafaelw):
+        // https://github.com/Polymer/polymer-expressions/issues/21
+        var updateObserver = true; //self.dynamicDeps;
+        if (updateObserver)
           observer.startReset();
 
         var value = self.getValue(model,
-                                  self.dynamicDeps ? observer : undefined,
+                                  updateObserver ? observer : undefined,
                                   filterRegistry);
-        if (self.dynamicDeps)
+        if (updateObserver)
           observer.finishReset();
 
         return value;

tests/tests.js

@@ -969,6 +969,35 @@ suite('PolymerExpressions', function() {
     });
   });
 
+  test('computed - newly reachable objects', function(done) {
+    var div = createTestHtml(
+        '<template bind>' +
+            '<div foo="{{ 1 == foo.bar.bat }}">' +
+        '</template>');
+
+    var model = {};
+
+    recursivelySetTemplateModel(div, model);
+
+    then(function() {
+      assert.equal('false', div.childNodes[1].getAttribute('foo'));
+      model.foo = {};
+
+    }).then(function() {
+      assert.equal('false', div.childNodes[1].getAttribute('foo'));
+      model.foo.bar = {};
+
+    }).then(function() {
+      assert.equal('false', div.childNodes[1].getAttribute('foo'));
+      model.foo.bar.bat = 1;
+
+    }).then(function() {
+      assert.equal('true', div.childNodes[1].getAttribute('foo'));
+
+      done();
+    });
+  });
+
 
   test('computed property with ident index', function(done) {
     var div = createTestHtml(