Merge "Skip the partition search for still frames"

diff --cc vp9/encoder/vp9_encodeframe.c
Simple merge

diff --cc vp9/encoder/vp9_encoder.c
Simple merge

diff --cc vp9/encoder/vp9_encoder.h
Simple merge

diff --cc vp9/encoder/vp9_speed_features.c
Simple merge

diff --cc vp9/encoder/vp9_speed_features.h
Simple merge