GitLab

iOS builds now default to 64-bit (codereview.chromium.org/1021513002). Bump
default device to iPhone 5s, which supports 64-bit binaries.

BUG=None
TEST=iossim works without passing any device flags.

Review URL: https://codereview.chromium.org/1070753004

Cr-Commit-Position: refs/heads/master@{#324283}