Reorganize some pub libraries.

sdk/lib/_internal/pub/lib/src/solver/version_solver.dart

Index: sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
diff --git a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart b/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
index 9a98698e8a10a67f7effb61366777bd21e02e3a8..2dc215e1c62b94327ae8086a4c22604b59d9d111 100644
--- a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
+++ b/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
@@ -2,7 +2,7 @@
 // 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.
 
-library version_solver;
+library pub.solver.version_solver;
 
 import 'dart:async';
 import 'dart:json' as json;
@@ -196,6 +196,8 @@ abstract class SolveFailure implements ApplicationException {
     return buffer.toString();
   }
 
+  String get message => toString();
+
   /// A message describing the specific kind of solve failure.
   String get _message {
     throw new UnimplementedError("Must override _message or toString().");