Revert of [DevTools] Inject element into toolbox window, do not load modules there. (patchset #2 id:150001 of https://codereview.chromium.org/653613002/)

Reason for revert:
Breaks all references to "document".

Original issue's description:
> [DevTools] Inject element into toolbox window, do not load modules there.
> 
> BUG=none
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=183669

TBR=pfeldman@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=none

Review URL: https://codereview.chromium.org/660503002

git-svn-id: svn://svn.chromium.org/blink/trunk@183744 bbb929c8-8fbe-4397-9dbb-9b2b20218538