Add emptiness test for CharBuffer

Test: atest CharBufferTest
Bug: 296827236
(cherry picked from https://android-review.googlesource.com/q/commit:e5926815c45f241ce7b4eeabae8b12fccf1bf42f)
Merged-In: I77efd3f55bdb86701e0be850359a8aa917c5e6a8
Change-Id: I77efd3f55bdb86701e0be850359a8aa917c5e6a8
1 file changed