sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 5547397958885d01c71a201e44eef4d18a389458..8b50c3aa50fd512643af32337e2f5c42bb5eca6f 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -6938,21 +6938,43 @@ class CssViewportRule extends CssRule {
 
 @DomName('CustomEvent')
 class CustomEvent extends Event {
+  var _dartDetail;
+
   factory CustomEvent(String type,
       {bool canBubble: true, bool cancelable: true, Object detail}) {
 
     final CustomEvent e = document._createEvent('CustomEvent');
 
-    e._initCustomEvent(type, canBubble, cancelable, detail);
+    e._dartDetail = detail;
+
+    // Only try setting the detail if it's one of these types to avoid
+    // first-chance exceptions. Can expand this list in the future as needed.
+    if (detail is List || detail is Map || detail is String || detail is num) {
+      try {
+        e._initCustomEvent(type, canBubble, cancelable, detail);
+      } catch(_) {
+        e._initCustomEvent(type, canBubble, cancelable, null);
+      }
+    } else {
+      e._initCustomEvent(type, canBubble, cancelable, null);
+    }
 
     return e;
   }
+
+  @DomName('CustomEvent.detail')
+  get detail {
+    if (_dartDetail != null) {
+      return _dartDetail;
+    }
+    return _detail;
+  }
   // To suppress missing implicit constructor warnings.
   factory CustomEvent._() { throw new UnsupportedError("Not supported"); }
 
   @DomName('CustomEvent.detail')
   @DocsEditable()
-  Object get detail native "CustomEvent_detail_Getter";
+  Object get _detail native "CustomEvent_detail_Getter";
 
   @DomName('CustomEvent.initCustomEvent')
   @DocsEditable()