dart2js: fix for https://github.com/dart-lang/sdk/issues/24412

pkg/compiler/lib/src/js_backend/codegen/codegen.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;
 
 import 'glue.dart';
 
 import '../../closure.dart' show ClosureClassElement;
 import '../../common/codegen.dart' show CodegenRegistry;
@@ skipping 621 matching lines @@
   }
 
   @override
   void visitUnreachable(tree_ir.Unreachable node) {
     // Output nothing.
     // TODO(asgerf): Emit a throw/return to assist local analysis in the VM?
   }
 
   @override
   void visitTry(tree_ir.Try node) {
+    void register(ClassElement classElement) {
+      if (classElement == null) return;
+      registry.registerInstantiatedClass(classElement);
+    }
+    // We might catch JavaScript exceptions.
+    register(glue.jsPlainJavaScriptObjectClass);
+    register(glue.jsUnknownJavaScriptObjectClass);
+
     js.Block tryBlock = buildBodyBlock(node.tryBody);
     tree_ir.Variable exceptionVariable = node.catchParameters.first;
     js.VariableDeclaration exceptionParameter =
         new js.VariableDeclaration(getVariableName(exceptionVariable));
     js.Block catchBlock = buildBodyBlock(node.catchBody);
     js.Catch catchPart = new js.Catch(exceptionParameter, catchBlock);
     accumulator.add(new js.Try(tryBlock, catchPart, null));
   }
 
   @override
@@ skipping 263 matching lines @@
   js.Expression visitAwait(tree_ir.Await node) {
     return new js.Await(visitExpression(node.input));
   }
 
   visitFunctionExpression(tree_ir.FunctionExpression node) {
     // FunctionExpressions are currently unused.
     // We might need them if we want to emit raw JS nested functions.
     throw 'FunctionExpressions should not be used';
   }
 }