Fix Renderer11 signed/unsigned warning in 32-bit. Change-Id: I1e11f54b0ae245cdd7e090ab0748821738ad6314 Reviewed-on: https://chromium-review.googlesource.com/218761 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>