Add CheckedRange<> and its test

Add CheckedRange<> and its test.

TEST=util_test CheckedRange
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/d05166c26c9f

[Robert Sesek, 2014-08-14 20:55:52]

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h
File util/numeric/checked_range.h (right):

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h...
util/numeric/checked_range.h:62: base::CheckedNumeric<ValueType>
checked_base_(base_);
No underscore at the end of checked_base_, or on line 66.

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h...
util/numeric/checked_range.h:67: static_cast<ValueType>(size_));
This read "fishy" for me for me, so I spent 10 minutes looking at this line. I
think you can more succinctly write this function, and have it read safer, as:

  bool IsValid() const {
    if (!base::IsValueInRangeForNumericType<ValueType, SizeType>(size_)) {
      return false;
    }
    base::CheckedNumeric<ValueType> checked_end(base_);
    checked_end += static_cast<ValueType>(size_);
    return checked_end.IsValid();
  }

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h...
util/numeric/checked_range.h:84: return value >= base_ && value < end();
Why base_ but end() ?

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h...
util/numeric/checked_range.h:104: return that.base_ >= base_ && that.end() <=
end();
Same.

[Mark Mentovai, 2014-08-14 23:12:01]

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h
File util/numeric/checked_range.h (right):

https://codereview.chromium.org/467113002/diff/1/util/numeric/checked_range.h...
util/numeric/checked_range.h:67: static_cast<ValueType>(size_));
rsesek wrote:
> This read "fishy" for me for me, so I spent 10 minutes looking at this line. I
> think you can more succinctly write this function, and have it read safer, as:
> 
>   bool IsValid() const {
>     if (!base::IsValueInRangeForNumericType<ValueType, SizeType>(size_)) {
>       return false;
>     }
>     base::CheckedNumeric<ValueType> checked_end(base_);
>     checked_end += static_cast<ValueType>(size_);
>     return checked_end.IsValid();
>   }

Yup, that’s better!

[Robert Sesek, 2014-08-15 03:06:34]

LGTM

[Mark Mentovai, 2014-08-15 17:22:39]

Committed patchset #2 manually as d05166c26c9f (presubmit successful).