Re-land: gpu: Make in-process default service global
This is a minor clean up to avoid creating/destroying multiple gpu
threads when using the in-process command buffer. Removes some
complexity in code and keeps a consistent thread id, just like the
cross-process command buffer.
BUG=
Previous committed: https://crrev.com/
496ecd8d62b325362409272c6b26fb027e640786
Previous Cr-Commit-Position: refs/heads/master@{#305782}
Reland include valgrind suppressions.
Review URL: https://codereview.chromium.org/
727093004
Cr-Commit-Position: refs/heads/master@{#306007}