Throw an exception when denying access to 'Frame's 'location' setter.

Source/core/dom/ErrorEvent.h

Index: Source/core/dom/ErrorEvent.h
diff --git a/Source/core/dom/ErrorEvent.h b/Source/core/dom/ErrorEvent.h
index 821554452fb4a24decb2d92844213b9222475257..f97491cd5b25e090ed4d76abdd77a1e7541a731b 100644
--- a/Source/core/dom/ErrorEvent.h
+++ b/Source/core/dom/ErrorEvent.h
@@ -65,19 +65,29 @@ public:
     }
     virtual ~ErrorEvent();
 
-    const String& message() const { return m_message; }
+    // As 'message' is exposed to JavaScript, prefer 'sanitizedMessage()' when present.
+    const String& message() const { return !sanitizedMessage().isEmpty() ? sanitizedMessage() : unsanitizedMessage(); }
     const String& filename() const { return m_fileName; }
     unsigned lineno() const { return m_lineNumber; }
     unsigned colno() const { return m_columnNumber; }
 
+    // 'messageForConsole' is not exposed to JavaScript, and prefers 'unsanitizedMessage()'.
+    const String& messageForConsole() const { return !unsanitizedMessage().isEmpty() ? unsanitizedMessage() : sanitizedMessage(); }
+
     virtual const AtomicString& interfaceName() const;
 
+    void setUnsanitizedMessage(const String&);
+
 private:
     ErrorEvent();
     ErrorEvent(const String& message, const String& fileName, unsigned lineNumber, unsigned columnNumber);
     ErrorEvent(const AtomicString&, const ErrorEventInit&);
 
-    String m_message;
+    const String& unsanitizedMessage() const { return m_unsanitizedMessage; }
+    const String& sanitizedMessage() const { return m_sanitizedMessage; }
+
+    String m_unsanitizedMessage;
+    String m_sanitizedMessage;
     String m_fileName;
     unsigned m_lineNumber;
     unsigned m_columnNumber;