Disable auto "debugger" call for tests

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

Index: pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.dart b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.dart
index 0f8d0b407f7c1577156d7aa6c405b79e426da9c4..49bc1cc11afb09fdf88249a0a93b02af77434ae4 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.dart
@@ -3,41 +3,48 @@
 // BSD-style license that can be found in the LICENSE file.
 part of dart._runtime;
 
+bool _trapRuntimeErrors = true;
+
+// Override, e.g., for testing
+void trapRuntimeErrors(bool flag) {
+  _trapRuntimeErrors = flag;
+}
+
 throwCastError(object, actual, type) => JS('', '''(() => {
-  debugger;
-  $throw_(new $CastErrorImplementation($object,
-                                       $typeName($actual),
-                                       $typeName($type)));
+  var found = $typeName($actual);
+  var expected = $typeName($type);
+  if ($_trapRuntimeErrors) debugger;
+  $throw_(new $CastErrorImplementation($object, found, expected));
 })()''');
 
 throwTypeError(object, actual, type) => JS('', '''(() => {
-  debugger;
-  $throw_(new $TypeErrorImplementation($object,
-                                       $typeName($actual),
-                                       $typeName($type)));
+  var found = $typeName($actual);
+  var expected = $typeName($type);
+  if ($_trapRuntimeErrors) debugger;
+  $throw_(new $TypeErrorImplementation($object, found, expected));
 })()''');
 
 throwStrongModeCastError(object, actual, type) => JS('', '''(() => {
-  debugger;
-  $throw_(new $StrongModeCastError($object,
-                                   $typeName($actual),
-                                   $typeName($type)));
+  var found = $typeName($actual);
+  var expected = $typeName($type);
+  if ($_trapRuntimeErrors) debugger;
+  $throw_(new $StrongModeCastError($object, found, expected));
 })()''');
 
 throwStrongModeTypeError(object, actual, type) => JS('', '''(() => {
-  debugger;
-  $throw_(new $StrongModeTypeError($object,
-                                   $typeName($actual),
-                                   $typeName($type)));
+  var found = $typeName($actual);
+  var expected = $typeName($type);
+  if ($_trapRuntimeErrors) debugger;
+  $throw_(new $StrongModeTypeError($object, found, expected));
 })()''');
 
 throwUnimplementedError(message) => JS('', '''(() => {
-  debugger;
+  if ($_trapRuntimeErrors) debugger;
   $throw_(new $UnimplementedError($message));
 })()''');
 
 throwAssertionError([message]) => JS('', '''(() => {
-  debugger;
+  if ($_trapRuntimeErrors) debugger;
   let error = $message != null
         ? new $AssertionErrorWithMessage($message())
         : new $AssertionError();
@@ -48,7 +55,7 @@ throwNullValueError() => JS('', '''(() => {
   // TODO(vsm): Per spec, we should throw an NSM here.  Technically, we ought
   // to thread through method info, but that uglifies the code and can't
   // actually be queried ... it only affects how the error is printed.
-  debugger;
+  if ($_trapRuntimeErrors) debugger;
   $throw_(new $NoSuchMethodError(null,
       new $Symbol('<Unexpected Null Value>'), null, null, null));
 })()''');