libutils: fix overflow in String8::allocFromUTF8

Patch contributed in:
https://code.google.com/p/android/issues/detail?id=182908

Bug: 23290056

(cherry picked from commit 4eeacbeec0ae66e9d9395abbf83666709f2e11e3)

Change-Id: Ife1dc0791040150132bea6884f1e6c8d31972d1b
(cherry picked from commit ebabef275283f771151ec93c17469374b789b2c8)
1 file changed