Revert of DevTools: simpleSelector should not contain nth-child specificity (https://codereview.chromium.org/183683023/)

Reason for revert:
Doesn't set a correct selector for elements with multiple classes, e.g. "<div class="foo bar baz/>"


Original issue's description:
> DevTools: simpleSelector should not contain nth-child specificity
> 
> This patch fixes DOMPresentationUtils.simpleSelector method to not
> include nth-child attribute.
> 
> BUG=349089
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168803

TBR=pfeldman@chromium.org,vsevik@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=349089

Review URL: https://codereview.chromium.org/198933003

git-svn-id: svn://svn.chromium.org/blink/trunk@169120 bbb929c8-8fbe-4397-9dbb-9b2b20218538
FlameChart: initial implementation for canvas grid.

BUG=
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/188683004

git-svn-id: svn://svn.chromium.org/blink/trunk@169121 bbb929c8-8fbe-4397-9dbb-9b2b20218538