Add UMA histogram for sticky keys.

BUG=335757

Review URL: https://codereview.chromium.org/131513014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250794 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250794
Test files for skip network check for offline enabled app.

Original CL: https://codereview.chromium.org/149843004/

TBR=tengs@chromium.org
BUG=333900

Review URL: https://codereview.chromium.org/155763009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250795 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250795