Process a cpp file.

def process_cpp(self, path, suffix):
        """Process a cpp file."""
        _cpplint_state.ResetErrorCounts()
        cpplint.ProcessFile(str(path), _cpplint_state.verbose_level)
        _cpplint_state.PrintErrorCounts()
        errors = _cpplint_state.errors_by_category.copy()

        if suffix == 'h':
            self.cpp_header_map[str(path)] = errors
        else:
            self.cpp_src_map[str(path)] = errors