Make the VM's dart:core and dart:async library patches clean.

sdk/lib/core/errors.dart

Index: sdk/lib/core/errors.dart
diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
index c11ea2e1a97da25e0c73490a216d7ec025492dc6..6f4fc5068d8945314b56cf03c438c654bce3b06b 100644
--- a/sdk/lib/core/errors.dart
+++ b/sdk/lib/core/errors.dart
@@ -414,6 +414,8 @@ class IndexError extends ArgumentError implements RangeError {
  */
 class FallThroughError extends Error {
   FallThroughError();
+
+  external String toString();
 }
 
 /**
@@ -421,8 +423,9 @@ class FallThroughError extends Error {
  */
 class AbstractClassInstantiationError extends Error {
   final String _className;
-  AbstractClassInstantiationError(String this._className);
-  String toString() => "Cannot instantiate abstract class: '$_className'";
+  AbstractClassInstantiationError(String className) : _className = className;
+
+  external String toString();
 }
 
 
@@ -459,16 +462,11 @@ class NoSuchMethodError extends Error {
    * the signature of the method that would have been called if the parameters
    * had matched.
    */
-  NoSuchMethodError(Object receiver,
-                    Symbol memberName,
-                    List positionalArguments,
-                    Map<Symbol ,dynamic> namedArguments,
-                    [List existingArgumentNames = null])
-      : _receiver = receiver,
-        _memberName = memberName,
-        _arguments = positionalArguments,
-        _namedArguments = namedArguments,
-        _existingArgumentNames = existingArgumentNames;
+  external NoSuchMethodError(Object receiver,
+                             Symbol memberName,
+                             List positionalArguments,
+                             Map<Symbol, dynamic> namedArguments,
+                             [List existingArgumentNames = null]);
 
   external String toString();
 }