http/tests/security/xssAuditor/cookie-injection.html is flaky

http/tests/security/xssAuditor/cookie-injection.html is flaky
https://bugs.webkit.org/show_bug.cgi?id=77908

Reviewed by Eric Seidel.

Before this patch, the output of this test depended on the state of the
global cookie store.  When running tests in parallel, the cookie store
is shared by multiple tests, and so its state varies from run to run.

This patch changes this test to look only for the specific cookie used
by this test, which should make the test more reliable when run in
parallel with other tests.

* http/tests/security/xssAuditor/cookie-injection-expected.txt:
* http/tests/security/xssAuditor/resources/echo-intertag.pl:
* platform/chromium/test_expectations.txt:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106906 268f45cc-cd09-0410-ab3c-d52691b4dbfc