Fix for Text fading on RTL app names is done at the beginning...

This is a fix for bug 10918591 [Android][bidid][HH] "Text fading on RTL
app names is done at the beginning of the text, not at the end."

The old logic for getting the fade edge was not symmetric with respect
to the text direction - when the text was centered, it basically
always placed the fade edge at the left, which of course is appropriate
for LTR text but not RTL. This patch makes the two paths symmetric
and sensitive to text direction.

Change-Id: Ief7604aeb659d474864468d2f102a53f5b43d09e