Fix comparison that overflows for addresses near uint max.

BUG=chromium:683578

Change-Id: I3f9b79eeeba3c68cccb72bd6423811c8ff8f2067
Reviewed-on: https://skia-review.googlesource.com/7410
Commit-Queue: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
2 files changed