Added nextIntRange to dartvm and dart2js.

Added nextIntRange to dartvm and dart2js. 

Adding implementation of nextIntRange to get the next int from a range.

BUG=

[floitsch, 2013-11-18 13:36:03]

Sorry this took so long.
If you are still up for it, LGTM after changing from nextIntRange to
nextIntInRange, and after the comments have been addressed.

https://codereview.chromium.org/11367087/diff/1/runtime/lib/math_patch.dart
File runtime/lib/math_patch.dart (right):

https://codereview.chromium.org/11367087/diff/1/runtime/lib/math_patch.dart#n...
runtime/lib/math_patch.dart:73: if (range <= 0) {
Doesn't test if max or min is negative.

https://codereview.chromium.org/11367087/diff/1/runtime/lib/math_patch.dart#n...
runtime/lib/math_patch.dart:74: throw new ArgumentError("min is greater then or
equal to max");
Would be nice to have the values in the error message.

https://codereview.chromium.org/11367087/diff/1/runtime/lib/math_patch.dart#n...
runtime/lib/math_patch.dart:76: range = nextInt(range);
I wouldn't have called the result of the random-call "range".

Either use a different variable, or just "return min + nextInt(range);".

https://codereview.chromium.org/11367087/diff/1/sdk/lib/_internal/compiler/im...
File sdk/lib/_internal/compiler/implementation/lib/math_patch.dart (right):

https://codereview.chromium.org/11367087/diff/1/sdk/lib/_internal/compiler/im...
sdk/lib/_internal/compiler/implementation/lib/math_patch.dart:59: if (min >=
max) throw new ArgumentError("min is greater then or equal to max");
80 chars. And the error message should contain the values.

https://codereview.chromium.org/11367087/diff/1/sdk/lib/_internal/compiler/im...
sdk/lib/_internal/compiler/implementation/lib/math_patch.dart:62: range =
nextInt(range);
Don't reuse the variable (which is not a range).
I would just write it in one line:
return min + nextInt(max - min);

https://codereview.chromium.org/11367087/diff/1/tests/lib/math/math2_test.dart
File tests/lib/math/math2_test.dart (right):

https://codereview.chromium.org/11367087/diff/1/tests/lib/math/math2_test.dar...
tests/lib/math/math2_test.dart:246: checkClose(5, r.nextIntRange(1, 10), 10);
checkClose is typed for doubles. This will throw in checked mode.

Check by hand that it is in the range.
Also: Add 3 more tests:
- one that has min negative: Expect.throws(...)
- one that has min == max.
- one that has min == max - 1. (just one value). and make sure the returned
value equals min.