diff -r 000000000000 -r 6474c204b198 netwerk/base/public/nsIContentSniffer.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/netwerk/base/public/nsIContentSniffer.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,35 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIRequest;
+
+/**
+ * Content sniffer interface. Components implementing this interface can
+ * determine a MIME type from a chunk of bytes.
+ */
+[scriptable, uuid(a5772d1b-fc63-495e-a169-96e8d3311af0)]
+interface nsIContentSniffer : nsISupports
+{
+  /**
+   * Given a chunk of data, determines a MIME type. Information from the given
+   * request may be used in order to make a better decision.
+   *
+   * @param aRequest The request where this data came from. May be null.
+   * @param aData Data to check
+   * @param aLength Length of the data
+   *
+   * @return The content type
+   *
+   * @throw NS_ERROR_NOT_AVAILABLE if no MIME type could be determined.
+   *
+   * @note Implementations should consider the request read-only. Especially,
+   * they should not attempt to set the content type property that subclasses of
+   * nsIRequest might offer.
+   */
+  ACString getMIMETypeFromContent(in nsIRequest aRequest,
+                                  [const,array,size_is(aLength)] in octet aData,
+                                  in unsigned long aLength);
+};