Reapply "Make patch file import declarations apply to the patched library too."

tests/compiler/dart2js_extra/math_lib_test.dart

Index: tests/compiler/dart2js_extra/math_lib_test.dart
diff --git a/samples/hi/hi.dart b/tests/compiler/dart2js_extra/math_lib_test.dart
similarity index 65%
copy from samples/hi/hi.dart
copy to tests/compiler/dart2js_extra/math_lib_test.dart
index 77cc144f834513f040b0496efde571b3ea84607a..8c3759ace6084a8cdc6b620f040ef484b43633ed 100644
--- a/samples/hi/hi.dart
+++ b/tests/compiler/dart2js_extra/math_lib_test.dart
@@ -2,10 +2,10 @@
 // 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('hi');
-
-#import('dart:html');
+#library("math_lib_test");
+#import("dart:math");
 
 main() {
-  document.query('#status').innerHTML = 'Hi, Dart';
+  Expect.equals(2.0, sqrt(4));
+  Expect.equals(2.25, pow(1.5, 2.0));
 }