Fix SignedExchangeRequestHandlerBrowserTest on Android KitKat

Setting a mock ContentBrowserClient via SetBrowserClientForTesting
doesn't work on Android KitKat. (crbug.com/864403)

After this patch, VariantMatch and VariantMismatch test cases will be
skipped in Android version < 5.

Bug: 937930,864403
Change-Id: Ia246305fbaa906c9a3f44d45b85e6b6e69b35d1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1501954
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Kunihiko Sakamoto <ksakamoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637609}
1 file changed