Summary:The default value for fontSizeMultiplier was zero. Although this was usually overriden with the correct value (typically 1.0), it sometimes wasn't resulting in a divide-by-zero in the text height calculation.
This diff corrects that bug by setting 1.0 as the default, and guarding against zero values being set.
I also fixed some suspicious logic that seemed to assume the result of BOOL && CGFloat would be 0 or the CGFloat value, which is true in JS but not in C (it would always be 0 or 1).
Reviewed By: javache
Differential Revision: D3179196
fb-gh-sync-id: cc09b104c9087fc1a2f45d8d3f70af221c2ad823
fbshipit-source-id: cc09b104c9087fc1a2f45d8d3f70af221c2ad823
362738a776