Fix nit which is unefficiant sequence to deleteMarkedNodes.

deleteMarkedNodes need to move postion to prevent unefficiant do while loop.

BUG=none

Review URL: https://codereview.chromium.org/246793004

git-svn-id: svn://svn.chromium.org/blink/trunk@172279 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add flaky line for editing/selection/4960116.html.

tbr/notry since this is killing the commit queue.

TBR=tkent@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/246753005

git-svn-id: svn://svn.chromium.org/blink/trunk@172280 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DevTools] Minor tweak in popover positioning.

When positioning popover below anchor, the visible bottom coordinate was wrong: |arrowHeight - borderWidth| instead of |borderRadius|.
Consequently, it caused wrong position update, and popover did extend below container element, which is unacceptable and leads to bad layout.

BUG=363535

Review URL: https://codereview.chromium.org/246823003

git-svn-id: svn://svn.chromium.org/blink/trunk@172281 bbb929c8-8fbe-4397-9dbb-9b2b20218538