[Mac] Move NSColor sandbox warmup to only happen for ppapi.

This is not needed for renderers, and should be scoped to the right process
type.

BUG=348304,306348
TEST=Flash and renderers do not crash.

Review URL: https://codereview.chromium.org/186803004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255612 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255612