Prior to this patch, we failed to honor:
* margin-left on elements in inline layout with 0 width and 0 height
* margin-right on elements in inline layout with 0 width
I think that was because the code in CanPlaceFrame to discard both
margins when the width was 0 was running after the left-margin was
applied, unless the later code in PlaceFrame (checking both width 0 and
height 0) un-applied that left margin.
The assertion count change in test_value_computation.html is due to 2
additional "bad width" assertions (I presume from honoring large
margins that were previously ignored).
The change to 538935-1-ref.html is to match an improvement in rendering
of the margins in the test, where both sides of the margin are now
honored.
The change to layout/reftests/text-overflow/marker-basic-ref.html is to
keep the reference (which uses margins) rendering the same way following
the changes to margin handling.
The new behavior (in the reftests added in layout/reftests/inline/)
matches at least Chromium; I didn't check any other browsers.
