Build errors on Linux:

error: comparison of integers of different signs: 'const int' and 'const unsigned int'

BUG=angleproject:991
BUG=478570

This reverts commit f1ae954b.

Change-Id: I217aba1b32dc0e70d6153337a1f0ccef0483a0e1
Reviewed-on: https://chromium-review.googlesource.com/268792Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>