Sandbox initialization for VideoToolbox.

Creates a VideoToolbox decompression session during sandbox startup so that VideoToolbox can load all of its libraries before the sandbox goes into effect.

Note: Once this CL is committed, VTVideoDecodeAccelerator can be enabled using only --ignore-gpu-blacklist.

BUG=133828

Review URL: https://codereview.chromium.org/723993003

Cr-Commit-Position: refs/heads/master@{#305938}
3 files changed