Fix some problems in SessionManager in chromoting
Fix some problems in SessionManager in chromoting

SessionManager doesn't handle empty dirty rect list, this is fixed in this patch.

This patch also make SessionManager handle rate controlling better.

Review URL: http://codereview.chromium.org/3127019

git-svn-id: http://src.chromium.org/svn/trunk/src@56605 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 6d8e5005db59bd43a26b9683025428e9b3412620
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