Remove main frame overflow from some non-scrollbar tests

Turning on force compositing mode causes tiny scrollbar rendering
differences when run through Mesa.  These are small one bit in color
changes smeared over two pixels so are likely filtering issues.  Rather
than rebaseline every test that needs to be updated due to this
rendering issue, instead remove overflow from a large number of tests
that don't actually need scrollbars for correctness.

I looked through all the tests and verified that their pixel output
still looks correct and that the only visual change is removed
scrollbars and layout changes resulting from that.

Scrollbars in general cause image rebaselines over time, so this should
help cut down on future changes too.

BUG=361729

Review URL: https://codereview.chromium.org/249723003

git-svn-id: svn://svn.chromium.org/blink/trunk@172422 bbb929c8-8fbe-4397-9dbb-9b2b20218538