In large-scale tile coding, when the number of tiles is large and the tile
size is small, using a fixed number of bytes in the tile header to store
tile-data size information as done in current VP9 codec would bring high
overhead for each tile. This patch implemented 2 ways to lower that overhead
and adaptively determine the number of bytes needed for tile-data size
transmission.
The test on a test clip having the tile size of 64x64 showed that the number
of bytes used for storing tile-data size was reduced from 4 to 1, which
substantially improved the compression ratio in large-scale tile coding.
Change-Id: Ia02fc43eda67fa252fbc2554321957790f53f6fd
15a90668a5