For tests that scroll the top-level FrameView and then dump the
layout tree (the default behavior), we expect the frame-level scroll
to be reflected in the positions of all layers; for example:
    
 layer at (0,0) size 800x600 scrollX 1255.00 scrollY 1023.00 scrollWidth 2055 scrollHeight 2063
   LayoutView at (0,0) size 800x600
-layer at (0,0) size 800x2063 backgroundClip at (0,0) size 800x600 clip at (0,0) size 800x600
+layer at (-1255,-1023) size 800x2063 backgroundClip at (0,0) size 800x600 clip at (0,0) size 800x600
   LayoutBlockFlow {HTML} at (0,0) size 800x2063
     LayoutBlockFlow {BODY} at (8,8) size 784x2047
       LayoutBlockFlow {DIV} at (0,0) size 2047x2047
-layer at (8,8) size 784x0
+layer at (-1247,-1015) size 784x0
   LayoutBlockFlow {DIV} at (0,0) size 784x0
 scrolled to 1255,1023


Many of these tests were identified and rebaselined using pattern-matching on the layout tree dump:

https://chromium-review.googlesource.com/699752

However, some of the tests slipped through the regexp cracks.  They need to be manually inspected for correctness and rebaselined if correct.

A few example tests (not a complete list):

compositing/iframes/composited-iframe-scroll.html
compositing/iframes/iframe-copy-on-scroll.html
compositing/iframes/iframe-in-composited-layer.html
compositing/iframes/nested-iframe-scrolling.html
fast/events/autoscroll.html