Update {virtual,override} to follow C++11 style in gpu.

The Google style guide states that only one of {virtual,override,final} should be used for each declaration, since override implies virtual and final implies both virtual and override.

This patch was manually generated using a regex and a text editor.

NOTRY=true
BUG=417463

Review URL: https://codereview.chromium.org/1101013002

Cr-Commit-Position: refs/heads/master@{#326845}
1 file changed