Re-land of issue 200623006: Set geometry dirty bits on composited layer mappings w/squashing

LayoutTests/virtual/softwarecompositing/squashing/squashed-layer-loses-graphicslayer-expected.txt

 A squashing RenderLayer that becomes non-composited should correctly send a repaint invalidation to the new container GraphicsLayer that it paints into. When run interactively, hovering over the force-composited gray div should not cause other layers to disappear.
 
 CASE 1, original layer tree:
 (GraphicsLayer
   (bounds 800.00 600.00)
   (children 1
     (GraphicsLayer
       (bounds 800.00 600.00)
       (contentsOpaque 1)
       (drawsContent 1)
@@ skipping 12 matching lines @@
               (bounds 260.00 260.00)
               (drawsContent 1)
             )
           )
         )
       )
     )
   )
 )
 CASE 2, The original composited layer is no longer composited, which then also removes all squashing layers. The important point is that there should be an appropriate repaint to the root GraphicsLayer:
+(GraphicsLayer
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (drawsContent 1)
+      (repaint rects
+        (rect 60.00 60.00 100.00 100.00)
+        (rect 60.00 60.00 100.00 100.00)
+        (rect 0.00 0.00 100.00 100.00)
+        (rect 140.00 140.00 100.00 100.00)
+        (rect 0.00 0.00 100.00 100.00)
+        (rect 220.00 220.00 100.00 100.00)
+        (rect 0.00 0.00 100.00 100.00)
+        (rect 300.00 300.00 100.00 100.00)
+        (rect 140.00 140.00 100.00 100.00)
+        (rect 220.00 220.00 100.00 100.00)
+        (rect 300.00 300.00 100.00 100.00)
+      )
+    )
+  )
+)