Change FX_Alloc to FX_Try_Alloc in _JpegEncode

This CL is used for:
1. keeping the same logic as before (the behaviour
   of FX_Alloc was changed for OOM).
2. fixing a potential integer overflow.

BUG=N/A
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1126013006
1 file changed