Fix bug in VP8LCalculateEstimateForCacheSize.

The method VP8LCalculateEstimateForCacheSize is not evaluating the all possible
range for cache_bits.
Also added a small penality for choosing the larger cache-size. This is done to
strike a balance between additional memory/CPU cost (with larger cache-size) and
byte savings from smaller WebP lossless files.

This change saves about 0.07% bytes and speeds up compression by 8% (default
settings). There's small speedup at Q=50 along with byte savings as well.
Compression at Quality=25 is not effected by this change.

Change-Id: Id8f87dee6b5bccb2baa6dbdee479ee9cda8f4f77
Merge "Fix bug in VP8LCalculateEstimateForCacheSize."