Bug fix: internals.textSurroundingNode crashes when the node is NULL

Added NULL check.

BUG=354958
TEST=Check there is no crashes when the minimized test case is passed to
content_shell

Review URL: https://codereview.chromium.org/201573008

git-svn-id: svn://svn.chromium.org/blink/trunk@169849 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Allow DOM breakpoints on shadow DOM elements

R=pfeldman, vsevik
BUG=353916

Review URL: https://codereview.chromium.org/198713006

git-svn-id: svn://svn.chromium.org/blink/trunk@169851 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unnecessary workaround in universal-accelerated-overflow-scrolling.html.

The issue that required this workaround was fixed in
https://codereview.chromium.org/204983002/.

BUG=328156

Review URL: https://codereview.chromium.org/209963003

git-svn-id: svn://svn.chromium.org/blink/trunk@169853 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Add an option to get current stack without scopes.

Getting scopes info from V8 debugger takes significant time.
Sometimes we don't need the scopes at all, thus we can save on this expensive work.
For async stacks we will be getting "fast" scope chains: up to the Local scope only (coming soon).

R=yurys

Review URL: https://codereview.chromium.org/208263015

git-svn-id: svn://svn.chromium.org/blink/trunk@169854 bbb929c8-8fbe-4397-9dbb-9b2b20218538