Move Privet printer search timeout to Javascript

Remove timeout for privet printer search from C++ code and add it to Javascript
instead.

BUG=326718

Review URL: https://codereview.chromium.org/103803009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242568 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242568