Support for same prefix for multiple imports.

compiler/java/com/google/dart/compiler/resolver/LibraryPrefixElement.java

Index: compiler/java/com/google/dart/compiler/resolver/LibraryPrefixElement.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/LibraryPrefixElement.java b/compiler/java/com/google/dart/compiler/resolver/LibraryPrefixElement.java
new file mode 100644
index 0000000000000000000000000000000000000000..96486174bc46ba9289ade0c03885c6d1c8e1bbcf
--- /dev/null
+++ b/compiler/java/com/google/dart/compiler/resolver/LibraryPrefixElement.java
@@ -0,0 +1,13 @@
+// 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.
+
+package com.google.dart.compiler.resolver;
+
+import java.util.List;
+
+public interface LibraryPrefixElement extends EnclosingElement {
+  Scope getScope();
+  void addLibrary(LibraryElement library);
+  List<LibraryElement> getLibraries();
+}