Fix crashing issue when total vertical padding is larger than the View's height

[h6ah4i]

Hi. I noticed that AndroidFastScroll can cause weird app crashing in a certain situation.

The crash log message

Here's the extracted message from the Logcat when my app crashed.

I can see an error occurred in the RenderThread thread and someone trying to create a negative height (-196 px) View.

A/libc: Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 5715 (RenderThread), pid 5581 (***)
Abort message: 'JNI DETECTED ERROR IN APPLICATION: JNI CallVoidMethodV called with pending exception java.lang.IllegalStateException: Unable to create layer for View, size 64x-192 max size 16384 color type 4 has context 1
    (Throwable with empty stack trace)    

Investigation result

When FastScroller attached view's height is smaller than its total vertical padding, the track view created in FastScroller will be requested to layout with inappropriate coordinates.

Proposed fix

Cramping the bottom position value with the top position value not to request negative height when layout the track view.

[zhanghai]

Thanks for the fix and sorry I somehow forgot to take a look at this!

However, you will need to sign the CLA before I can merge this PR. If you don't want the trouble, I can also just go ahead and fix it myself. What do you think?

[h6ah4i]

@zhanghai Hi. Thank you for your response 👍

I think I have already signed the Google Individual Contributor License Agreement, can you confirm my agreement status?

[zhanghai]

Cool! I'll merge the fix, thanks!