[Regression fix] [Data URI parser] Accept data URI with invalid mediatype data

net/base/data_url.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // NOTE: based loosely on mozilla's nsDataChannel.cpp
 
 #include <algorithm>
 
 #include "net/base/data_url.h"
 
@@ skipping 48 matching lines @@
                iter->compare(0, kCharsetTagLength, kCharsetTag) == 0) {
       charset->assign(iter->substr(kCharsetTagLength));
       // The grammar for charset is not specially defined in RFC2045 and
       // RFC2397. It just needs to be a token.
       if (!net::HttpUtil::IsToken(*charset))
         return false;
     }
   }
 
   if (mime_type->empty()) {
-    // fallback to defaults if nothing specified in the URL:
+    // Fallback to the default if nothing specified in the mediatype part as
+    // specified in RFC2045. As specified in RFC2397, we use |charset| even if
+    // |mime_type| is empty.
     mime_type->assign("text/plain");
   } else if (!ParseMimeTypeWithoutParameter(*mime_type, NULL, NULL)) {
-    return false;
+    // Fallback to the default as recommended in RFC2045 when the mediatype
+    // value is invalid. For this case, we don't respect |charset| but force it
+    // set to "US-ASCII".
+    mime_type->assign("text/plain");
+    charset->assign("US-ASCII");
   }
   if (charset->empty())
     charset->assign("US-ASCII");
 
   // The caller may not be interested in receiving the data.
   if (!data)
     return true;
 
   // Preserve spaces if dealing with text or xml input, same as mozilla:
   //   https://bugzilla.mozilla.org/show_bug.cgi?id=138052
@@ skipping 40 matching lines @@
       temp_data.resize(length + padding_needed, '=');
     }
     return base::Base64Decode(temp_data, data);
   }
 
   temp_data.swap(*data);
   return true;
 }
 
 }  // namespace net