[Chrome OS] Make LoginLibrary robust to extraneous signals
[Chrome OS] Make LoginLibrary robust to extraneous signals

First step to allowing the session manager to handle whitelisting the owner.

BUG=chromium-os:7511
TEST=unit tests, install on device with ToT session_manager

Review URL: http://codereview.chromium.org/3671005

git-svn-id: http://src.chromium.org/svn/trunk/src@62350 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 1620a43d361f794e76e0e9fe6794bd4b418812a6
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser