Use faster IsDecimalDigit in the json parser
Use faster IsDecimalDigit in the json parser

BUG=

Review URL: https://codereview.chromium.org/974353002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#27019}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh