Rename RuntimeError to CyclicIntializationError, as per spec.

sdk/lib/core/errors.dart

 // Copyright (c) 2012, 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.core;
 
 class Error {
   const Error();
 
   /**
@@ skipping 211 matching lines @@
            "${Error.safeToString(modifiedObject)}.";
   }
 }
 
 
 class OutOfMemoryError implements Error {
   const OutOfMemoryError();
   String toString() => "Out of Memory";
 }
 
+
 class StackOverflowError implements Error {
   const StackOverflowError();
   String toString() => "Stack Overflow";
 }
 
 /**
- * Error thrown when a runtime error occurs.
+ * Error thrown when a lazily initialized variable cannot be initialized.
+ *
+ * A static/library variable with an initializer expression is initialized
+ * the first time it is read. If evaluating the initializer expression causes
+ * another read of the variable, this error is thrown.
  */
-class RuntimeError implements Error {
-  final message;
-  RuntimeError(this.message);
-  String toString() => "RuntimeError: $message";
+class CyclicInitializationError implements Error {
+  final String variableName;
+  const CyclicInitializationError([this.variableName]);
+  String toString() => variableName == null
+      ? "Reading static variable during its initialization"
+      : "Reading static variable '$variableName' during its initialization";
 }