Implement try/catch in the JS backend.

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library code_generator_dependencies;
 
 import '../js_backend.dart';
 import '../../dart2jslib.dart';
 import '../../js_emitter/js_emitter.dart';
 import '../../js/js.dart' as js;
@@ skipping 103 matching lines @@
 
   String getInterceptorName(Set<ClassElement> interceptedClasses) {
     return _backend.namer.nameForGetInterceptor(interceptedClasses);
   }
 
   js.Expression getInterceptorLibrary() {
     return new js.VariableUse(
         _backend.namer.globalObjectFor(_backend.interceptorsLibrary));
   }
 
+  FunctionElement getExceptionUnwrapper() {
+    return _backend.getExceptionUnwrapper();
+  }
+
+  FunctionElement getTraceFromException() {
+    return _backend.getTraceFromException();
+  }
+
   FunctionElement getCreateRuntimeType() {
     return _backend.getCreateRuntimeType();
   }
 
   FunctionElement getRuntimeTypeToString() {
     return _backend.getRuntimeTypeToString();
   }
 
   FunctionElement getTypeArgumentWithSubstitution() {
     return _backend.getGetRuntimeTypeArgument();
@@ skipping 28 matching lines @@
   js.Expression generateTypeRepresentation(DartType dartType,
                                            List<js.Expression> arguments) {
     int variableIndex = 0;
     js.Expression representation = _backend.rti.getTypeRepresentation(
         dartType,
         (_) => arguments[variableIndex++]);
     assert(variableIndex == arguments.length);
     return representation;
   }
 }