There are a few plugins in the wild that don't take any src attribute - they simply load the plugin from the mime type. Google Hangouts is an example.
Created attachment 202933 [details] Patch
<rdar://problem/13695911>
Comment on attachment 202933 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=202933&action=review > Source/WebCore/html/HTMLPlugInImageElement.cpp:649 > + if ((m_loadedUrl.isNull() || m_loadedUrl.isEmpty()) && !loadedMimeType().isEmpty()) { No need to write (m_loadedUrl.isNull() || m_loadedUrl.isEmpty()); that’s the same as m_loadedUrl.isEmpty().
Committed r150731: <http://trac.webkit.org/changeset/150731>