Add a DevTools command to create an isolated world for a given frame

DevTools already has the ability to run script in any execution context,
it' just can't by itself create an isolated world.  This patch adds that
ability.  We believe this will be useful for Headless chrome users who
whish to manipulate the dom.  They can already do this via devtools
protocol but running a script in an isolated world should be easier to
work with.

BUG=546953

Review-Url: https://codereview.chromium.org/2848653003
Cr-Commit-Position: refs/heads/master@{#470870}
9 files changed