Revert "Remove mouse cursor capturer from the ScreenCapturer interface"

This reverts commit 0adc4953512ee0a57cf7f3c0591b024c2316554a. It broke
FYI bots

TBR=sergeyu@chromium.org

Review URL: https://webrtc-codereview.appspot.com/27649004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7364 4adac7df-926f-26a2-2b94-8c16560cd09d