DevTools: Clean liveLocations stored in Linkifier when target is gone

BUG=

Review URL: https://codereview.chromium.org/365083002

git-svn-id: svn://svn.chromium.org/blink/trunk@177551 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [CodeMirror] fix indentation after "Enter" in certain cases

This patch fixes an error in BlockIndentController. The root cause of
the issue was the incorrect usage of String.prototype.substr method,
which for the negative values of the first argument returns
substrings starting from the line end.

BUG=391403

Review URL: https://codereview.chromium.org/363313006

git-svn-id: svn://svn.chromium.org/blink/trunk@177552 bbb929c8-8fbe-4397-9dbb-9b2b20218538