Take RTL layouts into account for bounding rect alignment

The bounding rects should take layout direction into consideration given
the App Header layout itself does, otherwise the rects won't match the
system elements in the header.

Fix: 375671209
Flag: EXEMPT bug fix
Test: Force RTL in dev settings, open Chrome with custom header in
freeform, check tabs align to the edges of the system elements

Change-Id: Ia12e431275bcf4182d9d11184e3fb19bfe159b68