Hide RenderBox::isBox() / RenderText::isText()

Source/core/rendering/RenderText.h

Index: Source/core/rendering/RenderText.h
diff --git a/Source/core/rendering/RenderText.h b/Source/core/rendering/RenderText.h
index fcb4ca838246269c5bac5e546eb619078bc63c72..97ab8febe31dd1530d9753d0f1a1ddb26a58c64f 100644
--- a/Source/core/rendering/RenderText.h
+++ b/Source/core/rendering/RenderText.h
@@ -182,6 +182,8 @@ private:
 
     void secureText(UChar mask);
 
+    bool isText() const WTF_DELETED_FUNCTION; // This will catch anyone doing an unnecessary check.
+
     // We put the bitfield first to minimize padding on 64-bit.
     bool m_hasBreakableChar : 1; // Whether or not we can be broken into multiple lines.
     bool m_hasBreak : 1; // Whether or not we have a hard break (e.g., <pre> with '\n').