Make type conversion explicit
Make type conversion explicit

This fixes a few compiler warnings for MSVC.

Change-Id: If4fa6eb3638e4cb92e982c7444e63fdc09c6f16e

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom