RenderGrid needs to pop its LayoutState before relayout.

Source/core/rendering/RenderFlowThread.cpp

Index: Source/core/rendering/RenderFlowThread.cpp
diff --git a/Source/core/rendering/RenderFlowThread.cpp b/Source/core/rendering/RenderFlowThread.cpp
index bbb67eb16f960af05d02491b75793bfc3a7f16d1..eef49e000b55142b372a3fea19c94a3bd4b41bff 100644
--- a/Source/core/rendering/RenderFlowThread.cpp
+++ b/Source/core/rendering/RenderFlowThread.cpp
@@ -309,6 +309,7 @@ void RenderFlowThread::pushFlowThreadLayoutState(const RenderObject& object)
         }
     }
 
+    ASSERT(!m_statePusherObjectsStack.contains(&object));
     m_statePusherObjectsStack.add(&object);
 }