JB_MR1: native/libs/ui: Adding fix for conf 2.0 seg faults

function call to cancelBuffer was resulted in seg-faults on conf 2.0.
Setting function pointer of cancelBuffer to null in order to select
correct path of execution.
CRs-fixed: 383715

Change-Id: I6de8355febaea86ded63f33a582c787fef862193
SurfaceFlinger: Change to support framebuffer flip for 2D blitters

- Surfaceflinger does not flip framebuffers when there are
  no layers marked for HWC_FRAMEBUFFER
- This change checks for the HWC_BLIT flag and will request a flip
  to a new FB_TARGET buffer even if there are no FRAMEBUFFER layers

Change-Id: I1cb44389a05c9ec049d7f0d39c288feccb11a91c