Switch 'unsigned int' to size_t to fix 64-bit Xcode builds

BRANCH=none
BUG=none
TEST=compilation succeeds

Change-Id: I09c95faad2dce8deb77ff1a0b3e008964c0b53f3
Signed-off-by: nagendra modadugu <ngm@google.com>
Reviewed-on: https://chromium-review.googlesource.com/400466
Commit-Ready: Nagendra Modadugu <ngm@google.com>
Tested-by: Nagendra Modadugu <ngm@google.com>
Reviewed-by: Andrey Pronin <apronin@chromium.org>
6 files changed