Enable preload=metadata lazy loading by default on Win, Android, Linux.

The results on macOS, CrOS platforms are noisy / aren't completely
regression free, so some further investigation is needed to understand
if there are actually issues there.

Improvements:
All: ~5% reduction in number of decoder instances.
All: ~9-12% reduction in the number of pipelines created.
Android, Win: ~15-32% reduction in number of unused players.
Android: A 15-20% reduction in GPU crashes.

Acceptable regressions:
All: ~2-8% _increase_ in time to first frame (tens of milliseconds).

BUG=879406
TEST=none
R=liberato

Change-Id: Id0d5b0490e31a7a2a21d314c0d4afcf98aad567e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1606965
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661914}
22 files changed