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

lib/compiler/implementation/lib/math.dartp

Index: lib/compiler/implementation/lib/math.dartp
diff --git a/lib/compiler/implementation/lib/math.dartp b/lib/compiler/implementation/lib/math.dartp
new file mode 100644
index 0000000000000000000000000000000000000000..2901563f4f5857f7beaff73530f1d104dbcbec79
--- /dev/null
+++ b/lib/compiler/implementation/lib/math.dartp
@@ -0,0 +1,12 @@
+// 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.
+
+// Patch file for dart:math library.
+
+// Imports the MathNatives class used by the library.
+#import("js_helper.dart");
+
+// Override the sqrt function, as proof-of-concept.
+double sqrt(num value)
+  => JS('double', @'Math.sqrt(#)', checkNum(value));