Revert 159421 - "Introduce ExecutionContextClient"

Also reverts the r159454 and r159430. And fixes a ton of style violations.

> This extracts most of the virtual functions from ScriptExecutionContext
> to newly introduced ExecutionContextClient interface, which Document
> and WorkerGlobalScope implement.
>
> ScriptExecutionContext::suspendActiveDOMObjects(),
> resumeActiveDOMObjects(), stopActiveDOMObjects() are devirtualized
> as there are no overrides of them.
>
> This is a preparation for decoupling ScriptExecutionContext
> from Document inheritance chain.
>
> BUG=305497
> TEST=none
> R=abarth@chromium.org, dglazkov@chromium.org, tkent@chromium.org


BUG=305497,306880
TBR=morrita@chromium.org

Review URL: https://codereview.chromium.org/27209003

git-svn-id: svn://svn.chromium.org/blink/trunk@159599 bbb929c8-8fbe-4397-9dbb-9b2b20218538