These are distinct from the renderer-level workarounds.

Add the first workaround, loseContextOnOutOfMemory. This is enabled
when the application enables reset notifications via KHR_robustness,
and is intended for more robust handling of errors in key APIs for
Chromium's correctness (in particular, sync objects).

Change Context::getResetStatus to persistently return the "lost" status
if it was set by calling Context::markContextLost. Previously, if
markContextLost was called but the implementation hadn't actually
received an error like a lost device, the "lost" reset status would be
dropped. Returning it only once to the caller is also fragile. Tested
this by manually injecting a failure in FenceSync11::clientWait and
ensuring that Chromium detected it as expected.

BUG=chromium:650138

Change-Id: Ie53069eacd1754ad5d64936e3fef315af24605fa
Reviewed-on: https://chromium-review.googlesource.com/394233
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>