Hooking up EncoderStateFeedback to handle intra requests instead of trigger ViEEncoder directly. This is one step towards adding send- and receive only channels and getting rid of the default module. BUG=769 Review URL: https://webrtc-codereview.appspot.com/824004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@2812 4adac7df-926f-26a2-2b94-8c16560cd09d