I figured out my problem.  I was trying to set the contextmenu attribute
of a DOM node to the ID of an element that had not been created yet.

- Jeremy

Jeremy Gillick wrote:
> I have an extension that uses an XCOM object (written in JavaScript)
> that causes these errors in a debug build:
>
> ###!!! ASSERTION: Missing master prototype. See bug 169036:
> 'mMasterPrototype', file
> /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/xul/document/src/nsXULDocument.cpp,
> line 653
> Break: at file
> /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/xul/document/src/nsXULDocument.cpp,
> line 653
> WARNING: NS_ENSURE_TRUE(mMasterPrototype) failed, file
> /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/xul/document/src/nsXULDocument.cpp,
> line 654
> WARNING: NS_ENSURE_TRUE(NS_SUCCEEDED(rv)) failed, file
> /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/base/src/nsGenericElement.cpp,
> line 3827
> WARNING: NS_ENSURE_TRUE(NS_SUCCEEDED(rv)) failed, file
> /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/base/src/nsGenericElement.cpp,
> line 3827
>
> My XPCOM object build a DOM structure on a DocumentFragment then holds
> it for the chrome code to use.  The chrome take the DocumentFragment
> node and clones it into the toolbar.  I know this seems like a lot of
> work, but it's how it has to be done in my case.
>
> Also, if I have the XPCOM code run, but turn off the chrome side, I
> don't get this error.  Does anybody know how an extension could
> generate this and how to prevent it?
>
> Thanks,
> Jeremy
>
>