Make ext-refs respect encoding flags.

The VP8_EFLAG_NO_UPD_LAST and VP8_EFLAG_NO_REF_LAST flags can be
passed to the encoder to signal that it should not update/reference
the LAST ref frame when encoding the current frame. With
--enable-ext-refs turned on, the new LAST2 LAST3 and LAST4 ref frames
could still be used or updated, which causes the
  VP10/ErrorResilienceTestLarge.DropFramesWithoutRecovery/{0,1,2}
tests to fail.

With this patch, if --enable-ext-refs is used, then
VP8_EFLAG_NO_UPD_LAST and VP8_EFLAG_NO_REF_LAST also applies to the
new LAST2 LAST3 and LAST4 ref frames, as well as the LAST ref frame.

Change-Id: If482b1c09bbaf914eca8e0348a2367bff261661d
3 files changed