Fix squashing to treat perspective and preserve3d elements as transform ancestors.

LayoutTests/compositing/squashing/squashing-inside-perspective-with-reparented-scrolling-expected.html

Index: LayoutTests/compositing/squashing/squashing-inside-perspective-with-reparented-scrolling-expected.html
diff --git a/LayoutTests/compositing/overflow/reparented-unclipped-overlay-scrollbars-with-offset-from-renderer.html b/LayoutTests/compositing/squashing/squashing-inside-perspective-with-reparented-scrolling-expected.html
similarity index 70%
copy from LayoutTests/compositing/overflow/reparented-unclipped-overlay-scrollbars-with-offset-from-renderer.html
copy to LayoutTests/compositing/squashing/squashing-inside-perspective-with-reparented-scrolling-expected.html
index 339be18ace9a3f1308889b685a42ed68ed664fe8..abf257b6a9cabcb0daa3303d64ce37e0fb19cefc 100644
--- a/LayoutTests/compositing/overflow/reparented-unclipped-overlay-scrollbars-with-offset-from-renderer.html
+++ b/LayoutTests/compositing/squashing/squashing-inside-perspective-with-reparented-scrolling-expected.html
@@ -27,13 +27,17 @@
     height: 500px;
 }
 </style>
+<div style="z-index: 1; position: absolute"></div>
+<div style="z-index: 0; perspective: 1000px; position: absolute;">
+    <div id='scroller'>
+        <div id='fixed'></div>
+        <div id='scrolled'></div>
+    </div>
+</div>
 <script>
 if (window.internals) {
     window.internals.settings.setOverlayScrollbarsEnabled(true);
     window.internals.settings.setPreferCompositingToLCDTextEnabled(true);
+    window.internals.settings.setLayerSquashingEnabled(false);
 }
 </script>
-<div id='scroller'>
-    <div id='fixed'></div>
-    <div id='scrolled'></div>
-</div>