[tools/android/loading] Helper script running Chrome on device with WPR

Review-Url: https://codereview.chromium.org/2687803004
Cr-Original-Commit-Position: refs/heads/master@{#453582}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d8eae749762d9b7f9f0e737b7a6c1ea2bc82aafe
4 files changed