DevTools: [CodeMirror] release checks for indent autodetection

Indent autodetection logic currently filters out indent candidates if
they occur in less then 1% of scanned lines. This patch increases this
number up to 3%.

As a drive-by, the patch fixes wrong indents in UIUtils.js (which
caused indent autodetection failure).

R=vsevik

Review URL: https://codereview.chromium.org/645163008

git-svn-id: svn://svn.chromium.org/blink/trunk@184099 bbb929c8-8fbe-4397-9dbb-9b2b20218538