IE's preventDefault is only right during event dispatch

Regression fix from #444

src/ShadowDOM/wrappers/events.js

@@ -537,14 +537,12 @@
 
       unsafeUnwrap(this).preventDefault();
 
-      if (!this.defaultPrevented) {
-        Object.defineProperty(this, 'defaultPrevented', {
-          get: function() {
-            return true;
-          },
-          configurable: true
-        });
-      }
+      Object.defineProperty(this, 'defaultPrevented', {
+        get: function() {
+          return true;
+        },
+        configurable: true
+      });
     };
   }
 

src/WebComponents/dom.js

@@ -67,14 +67,12 @@
 
       origPreventDefault.call(this);
 
-      if (!this.defaultPrevented) {
-        Object.defineProperty(this, 'defaultPrevented', {
-          get: function() {
-            return true;
-          },
-          configurable: true
-        });
-      }
+      Object.defineProperty(this, 'defaultPrevented', {
+        get: function() {
+          return true;
+        },
+        configurable: true
+      });
     };
   }
 

tests/WebComponents/html/dom.html

@@ -88,7 +88,32 @@
       e.preventDefault();
       assert.isTrue(e.defaultPrevented);
       // call again, just in case
-      assert.doesNotThrow(e.preventDefault);
+      assert.doesNotThrow(function() {e.preventDefault(); });
+    });
+
+    test('CustomEvent defaultPrevented', function() {
+      var e = new CustomEvent('foo', {cancelable: true});
+      e.preventDefault();
+      assert.isTrue(e.defaultPrevented);
+      // call again, just in case
+      assert.doesNotThrow(function() {e.preventDefault(); });
+    });
+
+    test('dispatch and prevent', function() {
+      var el = document.createElement('div');
+      document.body.appendChild(el);
+      var e = new CustomEvent('foo', {cancelable: true, bubbles: true});
+      var fn = function(e) {
+        e.preventDefault();
+      };
+      var check = function check(e) {
+        assert.isTrue(e.defaultPrevented);
+        document.body.removeEventListener('foo', check);
+        document.body.removeChild(el);
+      };
+      el.addEventListener('foo', fn);
+      document.body.addEventListener('foo', check);
+      assert.isTrue(e.defaultPrevented);
     });
   });
 </script>