Only exported functions should need tracing for debugging purposes.

BUG=18110152

Change-Id: I66c25db3954ef5e1aab5769b79a61336e8d95e73
Reviewed-on: https://swiftshader-review.googlesource.com/1243Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>