Added x86 apks and enabled x86 arch in run_cts script

This allows running WebView CTS tests on emulators
Bug:922854,923215

Test: Setup and launch an AVD (L-O) with sufficient internal storage (3GB ok),
Test: run_cts.py [-f "<test filter>"] [--fast-local-dev]

Change-Id: I644b3ca40962031f2ec3f495a028c4e5d0994db5
Reviewed-on: https://chromium-review.googlesource.com/c/1461680
Commit-Queue: Andrew Luo <aluo@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631846}
5 files changed