Never destroy the root content layer unless leaving compositing mode.

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp

Index: third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
index 8a5e5b8a42de264d2a1ea828b8ffe88c97fd6920..d222a3e50888812fe4eb33f19c654f271017d0d5 100644
--- a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
@@ -435,10 +435,10 @@ void PaintLayerCompositor::updateIfNeeded()
             GraphicsLayerTreeBuilder().rebuild(*updateRoot, ancestorInfo);
         }
 
-        if (childList.isEmpty())
-            destroyRootLayer();
-        else if (m_rootContentLayer)
+        if (!childList.isEmpty()) {
+            CHECK(m_rootContentLayer && m_compositing);
             m_rootContentLayer->setChildren(childList);
+        }
 
         applyOverlayFullscreenVideoAdjustmentIfNeeded();
     }