Reapply "Access to imports in the VM's runtime mirrors. Extend test coverage of the source mirrors."

tests/lib/mirrors/library_imports_b.dart

Index: tests/lib/mirrors/library_imports_b.dart
diff --git a/tests/compiler/dart2js/path with spaces/library space/lib with spaces.dart b/tests/lib/mirrors/library_imports_b.dart
similarity index 75%
copy from tests/compiler/dart2js/path with spaces/library space/lib with spaces.dart
copy to tests/lib/mirrors/library_imports_b.dart
index 16da6e3295bca2daa89abcf7104d7a492f7cd846..493f3239ae4211b96bcaa19ddfa87513ad8b8d16 100644
--- a/tests/compiler/dart2js/path with spaces/library space/lib with spaces.dart	
+++ b/tests/lib/mirrors/library_imports_b.dart
@@ -2,8 +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 spaces;
+library library_imports_b;
 
-part "part space/part space.dart";
-
-foo() => bar();
+var somethingFromB;
+var somethingFromBoth;