base: Update comment about use of std::numeric_limits.
base: Update comment about use of std::numeric_limits.

Mention that is also possible to use the (U)INTx_{MIN,MAX} macros from
stdint.h as well, when numeric_limits introduce static initializers.

See chromium-dev discussion in
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/Bvd9QU5pY9Q/discussion
for more details.

BUG=138542
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1337963002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#348528}

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