Defines and uses a kMaxSafeInteger macro (which expands to the constant
2^53-1) instead of accessing Number.MAX_SAFE_INTEGER. This saves loading
the attribute from the Number object, which is slightly faster. This also
makes it clearer from reading the code that tha value being compared is
constant.

BUG=
LOG=N

Review URL: https://codereview.chromium.org/1353953002

Cr-Commit-Position: refs/heads/master@{#30814}