Should updateCharacterBounds() throw an error if the bounds are out of range of the text?

[ltenmoz]

i.e. if rangeStart + characterBounds.length > text.length. See also #88.

[dandclark]

Chromium will need to add telemetry to verify that this change won't have too much of a compat impact. If it doesn't, then I'm in favor of doing this.