Oilpan: fix build after r197563.

Source/core/editing/VisibleSelection.cpp

Index: Source/core/editing/VisibleSelection.cpp
diff --git a/Source/core/editing/VisibleSelection.cpp b/Source/core/editing/VisibleSelection.cpp
index c9cc6bf0accd376bbe46a6713e4d3ae5178af2b0..d62a1378074750658edb84e8c55a8e17fc0ac307 100644
--- a/Source/core/editing/VisibleSelection.cpp
+++ b/Source/core/editing/VisibleSelection.cpp
@@ -1092,6 +1092,10 @@ DEFINE_TRACE(VisibleSelection)
     visitor->trace(m_extent);
     visitor->trace(m_start);
     visitor->trace(m_end);
+    visitor->trace(m_baseInComposedTree);
+    visitor->trace(m_extentInComposedTree);
+    visitor->trace(m_startInComposedTree);
+    visitor->trace(m_endInComposedTree);
     visitor->trace(m_changeObserver);
 }