Revert "Remove NullPointerException."

sdk/lib/core/exceptions.dart

Index: sdk/lib/core/exceptions.dart
diff --git a/sdk/lib/core/exceptions.dart b/sdk/lib/core/exceptions.dart
index ed16cf6c642c2c18ae2d1e9dc69dcd0d9708a8a9..61f3f89def79b09ac9016b15ec8100704051971a 100644
--- a/sdk/lib/core/exceptions.dart
+++ b/sdk/lib/core/exceptions.dart
@@ -40,6 +40,25 @@ class FormatException implements Exception {
 }
 
 
+class NullPointerException implements Exception {
+  const NullPointerException([this.functionName, this.arguments = const []]);
+  String toString() {
+    if (functionName == null) {
+      return exceptionName;
+    } else {
+      return "$exceptionName : method: '$functionName'\n"
+          "Receiver: null\n"
+          "Arguments: $arguments";
+    }
+  }
+
+  String get exceptionName => "NullPointerException";
+
+  final String functionName;
+  final List arguments;
+}
+
+
 class IllegalJSRegExpException implements Exception {
   const IllegalJSRegExpException(String this._pattern, String this._errmsg);
   String toString() => "IllegalJSRegExpException: '$_pattern' '$_errmsg'";