Add unittest for set next op index

In order to add this unittest, we need to ensure that a checkpoint is
saved after each InstallOp. However, current logic throttles checkpoint
by time, it also skips checkpoint if buffer offset is the same. To
address these issues,
        1. Add a ShouldCheckpoint() to control whether to throttle
        checkpoint based on time, unittest overrides this and just
        return true
        2. Modify logic to only skip a checkpoint if operation_index
        hasn't changed. For SOURCE_COPY operations, buffer offset won't
        be advanced but operation index will.

Test: treehugger
Change-Id: Ib81bfe0c4ecb7200096b4b22390fb1f2fcff1581

0 files changed, 0 insertions, 0 deletions