Remove the HasOwnBackingButPaintsIntoAncestor compositing state.

LayoutTests/TestExpectations

Index: LayoutTests/TestExpectations
diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
index bc0a36d05a9ad8b38d44f056f69975f6d75e3e83..e81f002b65466b7f0415197ce5dca13c6edfa74d 100644
--- a/LayoutTests/TestExpectations
+++ b/LayoutTests/TestExpectations
@@ -1,3 +1,7 @@
+crbug.com/418521 compositing/overflow/overflow-positioning.html [ NeedsRebaseline ]
+crbug.com/418521 virtual/prefer_compositing_to_lcd_text/compositing/overflow/overflow-positioning.html [ NeedsRebaseline ]
+crbug.com/418521 transforms/3d/point-mapping/3d-point-mapping-deep.html [ NeedsRebaseline ]
+crbug.com/418521 compositing/geometry/preserve-3d-switching.html [ NeedsRebaseline ]
 
 # This directly has manual tests that don't have to run with run-webkit-tests
 crbug.com/359838 http/tests/ManualTests/ [ Skip ]
@@ -753,7 +757,6 @@ crbug.com/334269 [ Mac ] svg/dynamic-updates/SVGForeignObjectElement-svgdom-widt
 crbug.com/334269 [ Mac ] svg/dynamic-updates/SVGImageElement-dom-height-attr.html [ NeedsManualRebaseline ]
 crbug.com/334269 [ Mac ] svg/dynamic-updates/SVGImageElement-dom-preserveAspectRatio-attr.html [ NeedsManualRebaseline ]
 crbug.com/334269 [ Mac ] svg/dynamic-updates/SVGImageElement-dom-width-attr.html [ NeedsManualRebaseline ]
-crbug.com/334269 [ Mac ] compositing/overflow/overflow-positioning.html [ NeedsManualRebaseline ]
 crbug.com/334269 [ Mac ] fast/backgrounds/animated-gif-as-background.html [ NeedsManualRebaseline ]
 crbug.com/334269 [ Mac ] fast/inline/justify-emphasis-inline-box.html [ NeedsManualRebaseline ]
 crbug.com/334269 [ Mac ] fast/repaint/box-shadow-h.html [ NeedsManualRebaseline ]