Force preload=none and disable autoplay on lowend Android devices.

Some older devices are unable to maintain multiple concurrent
players without borking the system badly enough that it needs
a reboot in order to continue playing media.

We also disable autoplay and preloading on low-memory devices to
avoid unnecessary codec churn.

BUG=612909, 622826
TEST=less crashy JB devices.

Review-Url: https://codereview.chromium.org/2344353003
Cr-Commit-Position: refs/heads/master@{#420073}
7 files changed