Prevent EndLayerOps when Begin was rejected

bug:30537130

BeginLayerOps were being rejected in a way that allowed the associated
EndLayerOps to still be recorded. This was a violation of DisplayList
content expectations, and caused crashes in FrameBuilder when trying to
play these DisplayLists back.

Change-Id: I531b840aa5c4ffb1ee458da3f4b366978eaeafbe