Fix bounds checking in CJS_PublicMethods::MakeRegularDate().

The function is looking ahead N characters at both its "format" and "value"
strings without validating that accesses are in bounds.  Add those validations.

There are also duplicate checks in the else-branches which re-test the inverse
of the if-branch.  These are removed for simplicity.

I also tidied some stray whitespace in the function while I was at it.

BUG=393831
R=jun_fang@foxitsoftware.com

Review URL: https://codereview.chromium.org/395303004
2 files changed