Disable data_reduction_proxy unit tests on iOS.

With the switch to WKWebView, Chrome on iOS code cannot use data
reduction proxy. Disable the tests on iOS as they are flaky and
make components_unittests falky on iOS.

BUG=658619

Review-Url: https://codereview.chromium.org/2450003002
Cr-Commit-Position: refs/heads/master@{#427432}
1 file changed