Blink: Move isolated world CSP handling to the core layer.

This CL moves the isolated world CSP handling from DOMWrapperWorld (at the
platform/bindings/layer) to the IsolatedWorldCSP singleton instance (at the
bindings/core layer). The platform/bindings layer doesn't know the concept of a
CSP, hence move it to the bindings/core/ layer. Furthermore, DOMWrapperWorld is
per world, hence it shouldn't necessarily store isolated world specific data.

This is required to store ContentSecurityPolicy instances for isolated worlds to
add CSP support for the isolated worlds. This CL should have no behavior change.

BUG=896041

Change-Id: I0ac995dbae549379934bfadeed148d4ca91c8706
Reviewed-on: https://chromium-review.googlesource.com/c/1354567
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612355}
9 files changed