Fix bugs supporting configuring DDC runtime settings before the application starts.

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.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;
 
-bool _trapRuntimeErrors = true;
-bool _ignoreWhitelistedErrors = true;
-bool _failForWeakModeIsChecks = true;
+// We need to set these properties while the sdk is only partially initialized
+// so we cannot use regular Dart fields.
+bool get _trapRuntimeErrors => JS('bool', 'dart.__trapRuntimeErrors');

[vsm, 2017/05/11 21:45:56]

Can you add a comment as to where these are now actually initialized?

+bool get _ignoreWhitelistedErrors =>
+    JS('bool', 'dart.__ignoreWhitelistedErrors');
+bool get _failForWeakModeIsChecks =>
+    JS('bool', 'dart.__failForWeakModeIsChecks');
 
 // Override, e.g., for testing
 void trapRuntimeErrors(bool flag) {
-  _trapRuntimeErrors = flag;
+  JS('', 'dart.__trapRuntimeErrors = #', flag);
 }
 
 void ignoreWhitelistedErrors(bool flag) {
-  _ignoreWhitelistedErrors = flag;
+  JS('', 'dart.__ignoreWhitelistedErrors = #', flag);
 }
 
 /// Throw an exception on `is` checks that would return an unsound answer in
 /// non-strong mode Dart.
 ///
 /// For example `x is List<int>` where `x = <Object>['hello']`.
 ///
 /// These checks behave correctly in strong mode (they return false), however,
 /// they will produce a different answer if run on a platform without strong
 /// mode. As a debugging feature, these checks can be configured to throw, to
 /// avoid seeing different behavior between modes.
 ///
 /// (There are many other ways that different `is` behavior can be observed,
 /// however, even with this flag. The most obvious is due to lack of reified
 /// generic type parameters. This affects generic functions and methods, as
 /// well as generic types when the type parameter was inferred. Setting this
 /// flag to `true` will not catch these differences in behavior..)
 void failForWeakModeIsChecks(bool flag) {
-  _failForWeakModeIsChecks = flag;
+  JS('', 'dart.__failForWeakModeIsChecks = #', flag);
 }
 
 throwCastError(object, actual, type) => JS(
     '',
     '''(() => {
   var found = $typeName($actual);
   var expected = $typeName($type);
   if ($_trapRuntimeErrors) debugger;
   $throw_(new $CastErrorImplementation($object, found, expected));
 })()''');
@@ skipping 59 matching lines @@
 })()''');
 
 throwNoSuchMethodError(
         receiver, memberName, positionalArguments, namedArguments) =>
     JS(
         '',
         '''(() => {
   if ($_trapRuntimeErrors) debugger;
   $throw_(new $NoSuchMethodError($receiver, $memberName, $positionalArguments, $namedArguments));
 })()''');