Assert that frame() derefs a non-null pointer.

Source/core/editing/Editor.h

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 123 matching lines @@
         bool isEnabled(Event* triggeringEvent = 0) const;
 
         TriState state(Event* triggeringEvent = 0) const;
         String value(Event* triggeringEvent = 0) const;
 
         bool isTextInsertion() const;
 
         // Returns 0 if this Command is not supported.
         int idForHistogram() const;
     private:
-        LocalFrame& frame() const { return *m_frame; }
+        LocalFrame& frame() const
+        {
+            ASSERT(m_frame);
+            return *m_frame;
+        }
 
         const EditorInternalCommand* m_command;
         EditorCommandSource m_source;
         RefPtrWillBeMember<LocalFrame> m_frame;
     };
     Command command(const String& commandName); // Command source is CommandFromMenuOrKeyBinding.
     Command command(const String& commandName, EditorCommandSource);
 
     // |Editor::executeCommand| is implementation of |WebFrame::executeCommand|
     // rather than |Document::execCommand|.
@@ skipping 84 matching lines @@
     bool m_shouldStartNewKillRingSequence;
     bool m_shouldStyleWithCSS;
     const OwnPtr<KillRing> m_killRing;
     VisibleSelection m_mark;
     bool m_areMarkedTextMatchesHighlighted;
     EditorParagraphSeparator m_defaultParagraphSeparator;
     bool m_overwriteModeEnabled;
 
     explicit Editor(LocalFrame&);
 
-    LocalFrame& frame() const { return *m_frame; }
+    LocalFrame& frame() const
+    {
+        ASSERT(m_frame);
+        return *m_frame;
+    }
 
     bool canDeleteRange(Range*) const;
 
     UndoStack* undoStack() const;
 
     bool tryDHTMLCopy();
     bool tryDHTMLCut();
     bool tryDHTMLPaste(PasteMode);
 
     bool canSmartReplaceWithPasteboard(Pasteboard*);
@@ skipping 32 matching lines @@
 
 inline bool Editor::markedTextMatchesAreHighlighted() const
 {
     return m_areMarkedTextMatchesHighlighted;
 }
 
 
 } // namespace blink
 
 #endif // Editor_h