Remove support for Javascript warnings in the VM.

runtime/lib/errors_patch.dart

Index: runtime/lib/errors_patch.dart
diff --git a/runtime/lib/errors_patch.dart b/runtime/lib/errors_patch.dart
index 59a61ec4bb9238f98da38db0bd605b63a7c3c224..0165ed9d83bf3ec4f1885b7124e8bee263488423 100644
--- a/runtime/lib/errors_patch.dart
+++ b/runtime/lib/errors_patch.dart
@@ -362,18 +362,3 @@ patch class NoSuchMethodError {
     return msg_buf.toString();
   }
 }
-
-class _JavascriptIntegerOverflowError extends Error {
-  final Object _value;
-
-  _JavascriptIntegerOverflowError(this._value);
-  String toString() => "Javascript Integer Overflow: $_value";
-}
-
-class _JavascriptCompatibilityError extends Error {
-  final String _msg;
-
-  _JavascriptCompatibilityError(this._msg);
-  String toString() => "Javascript Compatibility Error: $_msg";
-}
-