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This CL does two things:

1) exposes if Vulkan is enabled on chrome://gpu

2) adds vulkan feature which can be disabled by
gpu/config/software_rendering_list.json file based on environment.

Bug: 1002166,887018
Change-Id: Iee4b4e38e5e3761aeba1530a0d64d128f5aa9ae8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832293Reviewed-by: Jonathan Backer <backer@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702166}