mandoline sandbox: prewarm libraries before we raise the sandbox.
That was quick.
This moves back to a world where we don't perform dlopen() in the
sandbox. As is, we actually load other shared objects from our build
directories (html_viewer.mojo depends on libmedia_library.so, for
example), and the useage of things like base::SysInfo is too pervasive
throughout chrome to reasonably not so this.
BUG=492524
Review URL: https://codereview.chromium.org/
1264463005
Cr-Commit-Position: refs/heads/master@{#340989}