Revert of [chromedriver] Add shadow DOM support to chromedriver. (patchset #4 id:60001 of https://codereview.chromium.org/480483002/)

Reason for revert:
This CL breaks ElementEqualityTest.testAnElementFoundInADifferentFrameViaJsShouldHaveSameId and ElementFindingTest.testAnElementFoundInADifferentFrameViaJsCanBeUsed

Original issue's description:
> [chromedriver] Add shadow DOM support to chromedriver.
>
> BUG=chromedriver:852
>
> TEST= added some unit tests (beginning with testShadowDom) to chrome/test/chromedriver/test/run_py_tests.py
>
> R=samuong@chromium.org
>
> Committed: https://crrev.com/713e22356d84f46633890df2be12860b0d6a16ee
> Cr-Commit-Position: refs/heads/master@{#309002}

TBR=mcharsley@google.com
NOTREECHECKS=true
NOTRY=true
BUG=chromedriver:852

Review URL: https://codereview.chromium.org/824603002

Cr-Commit-Position: refs/heads/master@{#309398}