[Magnifier-35] Do not show when text is large

There is no point in displaying the magnifier when the text is large
enough. In this CL we are using the font metrics of the TextView to
decide whether the magnifier should be displayed or not.

Bug: 70608551
Test: manual testing
Change-Id: Icb2fb4412b6b930dfb3322e51fd0139152cf9d39
1 file changed