Implement try/catch in the JS backend.

pkg/compiler/lib/src/js_backend/codegen/glue.dart

Index: pkg/compiler/lib/src/js_backend/codegen/glue.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/glue.dart b/pkg/compiler/lib/src/js_backend/codegen/glue.dart
index 642e136927f90b42d2932f243a181a265b2e1bed..9dd74645e9100cadb49d8e7d9eebff883c54f347 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/glue.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/glue.dart
@@ -121,6 +121,14 @@ class Glue {
         _backend.namer.globalObjectFor(_backend.interceptorsLibrary));
   }
 
+  FunctionElement getExceptionUnwrapper() {
+    return _backend.getExceptionUnwrapper();
+  }
+
+  FunctionElement getTraceFromException() {
+    return _backend.getTraceFromException();
+  }
+
   FunctionElement getCreateRuntimeType() {
     return _backend.getCreateRuntimeType();
   }