Handle crash when submitting an injected form on an "image page".

Source/core/platform/network/FormDataBuilder.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 73 matching lines @@
     normalizedAcceptCharset.split(' ', charsets);
 
     WTF::TextEncoding encoding;
 
     Vector<String>::const_iterator end = charsets.end();
     for (Vector<String>::const_iterator it = charsets.begin(); it != end; ++it) {
         if ((encoding = WTF::TextEncoding(*it)).isValid())
             return encoding;
     }
 
+    if (document->inputEncoding().isEmpty()) {
+        if (document->defaultCharset().isEmpty())
+            return WTF::UTF8Encoding();
+
+        return document->defaultCharset();
+    }
+
     return document->inputEncoding();
 }
 
 Vector<char> FormDataBuilder::generateUniqueBoundaryString()
 {
     Vector<char> boundary;
 
     // The RFC 2046 spec says the alphanumeric characters plus the
     // following characters are legal for boundaries:  '()+_,-./:=?
     // However the following characters, though legal, cause some sites
@@ skipping 107 matching lines @@
         else if (c == '\n' || (c == '\r' && (i + 1 >= length || string.data()[i + 1] != '\n')))
             append(buffer, "%0D%0A");
         else if (c != '\r') {
             append(buffer, '%');
             appendByteAsHex(c, buffer);
         }
     }
 }
 
 }