Add kGoldenFrame and kOverlayFrame to FrameType

Add coding_index to EncodeFrameInfo
Add start_coding_index to GroupOfPicture
Add frame_coding_index_ to SimpleEncode

The definition of coding index is as follows.

Each show or no show frame is assigned with a coding index based
on its coding order (starting from zero) in the coding process of
the entire video. The coding index for each frame is unique.

Change-Id: I43e18434a0dff0d1cd6f927a693d6860e4038337
4 files changed