Add a flag to prohibit plurals/genders that don't take up the whole string.

pkg/intl/test/message_extraction/embedded_plural_text_before_test.dart

 // Copyright (c) 2014, 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.
 
-library really_fail_extraction_test;
+library embedded_plural_text_before_test;
 
 import "failed_extraction_test.dart";
 import "package:unittest/unittest.dart";
 
 main() {
-  test("Expect failure because warnings are errors", () {
-    runTestWithWarnings(warningsAreErrors: true, expectedExitCode: 1);
+  test("Expect failure because of embedded plural with text before it", () {
+    var files = ['embedded_plural_text_before.dart'];
+    runTestWithWarnings(warningsAreErrors: true, expectedExitCode: 1,
+        embeddedPlurals: false, sourceFiles: files);
   });
 }