Enable Try Dart to run on IE11.

site/try/src/leap.dart

Index: site/try/src/leap.dart
===================================================================
--- site/try/src/leap.dart	(revision 39366)
+++ site/try/src/leap.dart	(working copy)
@@ -31,6 +31,19 @@
 import 'user_option.dart' show
     UserOption;
 
+import 'settings.dart' show
+    alwaysRunInIframe,
+    communicateViaBlobs;
+
+bool isBrowserIE() {
+  return window.navigator.userAgent.contains(' Trident/7.0;');
+}
+
+initHiddenSettings() {
+  alwaysRunInIframe.setIfNotInitialized(isBrowserIE);
+  communicateViaBlobs.setIfNotInitialized(() => !isBrowserIE());
+}
+
 int count = 0;
 
 main() {
@@ -39,6 +52,8 @@
     currentSource = EXAMPLE_HELLO;
   }
 
+  initHiddenSettings();
+
   buildUI();
   ReceivePort port = new ReceivePort();
   Isolate.spawnUri(