VP9: Rate control update for re-encode screen-content.
VP9: Rate control update for re-encode screen-content.

For the re-encoding (at max-qp) on the detected high-content change:
update rate correction factor, reset rate over/under-shoot flags,
and update/reset the rate control for layered coding.

Change-Id: I5dc72bb235427344dc87b5235f2b0f31704a034a

ittiamvpx/libvpx-1,ittiamvpx/libvpx-1,shacklettbp/aom,thdav/aom,openpeer/libvpx_new,shacklettbp/aom,shacklettbp/aom,luctrudeau/aom,luctrudeau/aom,mwgoldsmith/libvpx,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,mwgoldsmith/vpx,jmvalin/aom,Topopiccione/libvpx,mbebenita/aom,GrokImageCompression/aom,mbebenita/aom,shacklettbp/aom,mwgoldsmith/vpx,thdav/aom,luctrudeau/aom,luctrudeau/aom,smarter/aom,ShiftMediaProject/libvpx,thdav/aom,jmvalin/aom,jmvalin/aom,mbebenita/aom,Topopiccione/libvpx,smarter/aom,webmproject/libvpx,jmvalin/aom,mbebenita/aom,ittiamvpx/libvpx-1,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mbebenita/aom,smarter/aom,openpeer/libvpx_new,Topopiccione/libvpx,smarter/aom,mbebenita/aom,mwgoldsmith/libvpx,luctrudeau/aom,openpeer/libvpx_new,webmproject/libvpx,shacklettbp/aom,mwgoldsmith/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,jmvalin/aom,smarter/aom,mbebenita/aom,ittiamvpx/libvpx-1,webmproject/libvpx,ittiamvpx/libvpx-1,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,GrokImageCompression/aom,mbebenita/aom,ShiftMediaProject/libvpx,smarter/aom,openpeer/libvpx_new,jmvalin/aom,mwgoldsmith/vpx,thdav/aom,mwgoldsmith/vpx,Topopiccione/libvpx,luctrudeau/aom,webmproject/libvpx,webmproject/libvpx,shacklettbp/aom,Topopiccione/libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,openpeer/libvpx_new,thdav/aom,thdav/aom,openpeer/libvpx_new,ShiftMediaProject/libvpx,mbebenita/aom,GrokImageCompression/aom