Fix: MultilineElment text value  won't update

Fix: MultilineElment text value  won't update in iPhone.

Issue:
1, Start the sample with iPhone(device or simulator), go to "Sample Controls" -> "Multiline".
2, Type some words and back.

Expected:
The label right to "Multiline" should show some of words typed in the step 2.

Actually:
There is nothing updated, the label in the right is blank.


This issue repro in iPhone, not in iPad.