gpu: Add crash key to tell if context is virtual.

Virtual contexts are used because of the blacklist but also dynamically
for platform specific reasons. It's hard to reason if the context is
virtual by looking at a crash report. This CL adds a crash key with that
information.

R=piman,alokp,rsesek,boliu,scottmg
BUG=724999

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I05333742ac98027545efeecc3e5311c390924a40
Reviewed-on: https://chromium-review.googlesource.com/556307
Reviewed-by: Scott Graham <[email protected]>
Reviewed-by: Alok Priyadarshi <[email protected]>
Reviewed-by: Antoine Labour <[email protected]>
Reviewed-by: Bo Liu <[email protected]>
Reviewed-by: Robert Sesek <[email protected]>
Commit-Queue: Sunny Sachanandani <[email protected]>
Cr-Commit-Position: refs/heads/master@{#483616}
11 files changed