WebPLog2FloorC: clear -Wshadow warning
WebPLog2FloorC: clear -Wshadow warning

log -> log_value

Change-Id: Iae7cea7e0875e59b0806de41eb0b58815307495e

PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp