ASSERT on renderer lifecycle

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index bbd53eedf4cffd918e1f61829cb4e775fa519cde..71fc7dd2476ee3370a4afa3e9d09da4a6d0fd10b 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -1102,6 +1102,8 @@ private:
 #endif
     const char* invalidationReasonToString(InvalidationReason) const;
 
+    static bool isAllowedToModifyRenderTreeStructure(Document&);
+
     RefPtr<RenderStyle> m_style;
 
     Node* m_node;
@@ -1275,6 +1277,18 @@ private:
     LayoutPoint m_previousPositionFromRepaintContainer;
 };
 
+// FIXME: remove this once the render object lifecycle ASSERTS are no longer hit.
+class DeprecatedDisableModifyRenderTreeStructureAsserts {
+    WTF_MAKE_NONCOPYABLE(DeprecatedDisableModifyRenderTreeStructureAsserts);
+public:
+    DeprecatedDisableModifyRenderTreeStructureAsserts();
+
+    static bool canModifyRenderTreeStateInAnyState();
+
+private:
+    TemporaryChange<bool> m_disabler;
+};
+
 // Allow equality comparisons of RenderObject's by reference or pointer, interchangeably.
 inline bool operator==(const RenderObject& a, const RenderObject& b) { return &a == &b; }
 inline bool operator==(const RenderObject& a, const RenderObject* b) { return &a == b; }