PVS-Studio warning V610 for Skia

inline SkFract SkFixedToFract(SkFixed x)
{
  SkASSERT(x >= (-2 << 16) && x <= (2 << 16) - 1);
  return x << 14;
}

This suspicious code was found in Skia project by PVS-Studio static code analyzer.
Warning message is:
V610 Undefined behavior. Check the shift operator '<<. The left operand '-2' is negative. skfixed.h 88

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/