Set auto breakpoint at various errors

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart

 // Copyright (c) 2015, 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.
 part of dart._runtime;
 
 /// This library defines a set of general javascript utilities for us
 /// by the Dart runtime.
 // TODO(ochafik): Rewrite some of these in Dart when possible.
 
 defineProperty(obj, name, desc) =>
     JS('', 'Object.defineProperty(#, #, #)', obj, name, desc);
 
 getOwnPropertyDescriptor(obj, name) =>
     JS('', 'Object.getOwnPropertyDescriptor(#, #)', obj, name);
 
 Iterable getOwnPropertyNames(obj) =>
     JS('', 'Object.getOwnPropertyNames(#)', obj);
 
 Iterable getOwnPropertySymbols(obj) =>
     JS('', 'Object.getOwnPropertySymbols(#)', obj);
 
 final hasOwnProperty = JS('', 'Object.prototype.hasOwnProperty');
 
+void debugger() {
+    JS('', 'debugger');
+}
+
 /// This error indicates a strong mode specific failure, other than a type
 /// assertion failure (TypeError) or CastError.
 void throwStrongModeError(String message) {
+  debugger();

[Jennifer Messerly, 2016/11/21 22:16:05]

same here, maybe just inline this:"

    JS('', 'debugger');

that way users get the breakpoint with one less stack frame to jump up.

[vsm, 2016/11/21 22:39:25]

Done.

   JS('', 'throw new #(#);', StrongModeErrorImplementation, message);
 }
 
 /// This error indicates a bug in the runtime or the compiler.
 void throwInternalError(String message) {
+  debugger();
   JS('', 'throw Error(#)', message);
 }
 
 getOwnNamesAndSymbols(obj) {
   var names = getOwnPropertyNames(obj);
   var symbols = getOwnPropertySymbols(obj);
   return JS('', '#.concat(#)', names, symbols);
 }
 
 safeGetOwnProperty(obj, String name) {
@@ skipping 67 matching lines @@
 }
 
 @JSExportName('export')
 exportProperty(to, from, name) => copyProperty(to, from, name);
 
 /// Copy properties from source to destination object.
 /// This operation is commonly called `mixin` in JS.
 copyProperties(to, from) {
   return copyTheseProperties(to, from, getOwnNamesAndSymbols(from));
 }