Previously, the`HTMLInputElement.selectinStart` and
`HTMLInputElement.selectionEnd` IDL setters, and the
`setRangeText()` IDL method were used when updating an input's value
on keyboard input. These methods can't be used for this purpose,
since selection doesn't apply to email type inputs. Therefore, this
change introduces internal-use only methods that don't check whether
selection applies to the given input.
