LayoutImpl contains state and should not have been static. Fixing this.

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@6584 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/user/src/com/google/gwt/layout/client/Layout.java b/user/src/com/google/gwt/layout/client/Layout.java
index 8d678de..483a805 100644
--- a/user/src/com/google/gwt/layout/client/Layout.java
+++ b/user/src/com/google/gwt/layout/client/Layout.java
@@ -317,7 +317,7 @@
     }
   }
 
-  private static LayoutImpl impl = GWT.create(LayoutImpl.class);
+  private LayoutImpl impl = GWT.create(LayoutImpl.class);
 
   private List<Layer> layers = new ArrayList<Layer>();
   private final Element parentElem;