Move VA-API warmup to sandboxing code.

This keeps all warmup-related code in the same place.

BUG=321209
TEST=falco boots, video works, histograms show acceleration works.
NOTRY=true

Review URL: https://codereview.chromium.org/79603003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236648 0039d316-1c4b-4281-b951-d872f2087c98
Added PrintPreview.RegeneratePreviewRequest.BeforeFirstData.

BUG=315315

Review URL: https://codereview.chromium.org/81473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236649 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236649