The layout test in platform/mac/plugins/pluginDocumentView-deallocated-dataSource.html no longer tests what it was designed to test. Firstly, it uses an iframe that points at a non-existent QuickTime file. Secondly, it relies on us using the QuickTime WebKit plug-in to handle full-frame QuickTime content. We switched to using the <video> element for this content a while back. The test should be updated to use a test WebKit plug-in that reproduces the original problem.
<rdar://problem/6697485>
I disabled this test in r41821.
Test is still present and marked as [ Skipped ] : https://searchfox.org/wubkat/source/LayoutTests/TestExpectations#3133 Considering that it is `plugin` related test and all plugin code is at least removed or not priority. I think it can be removed it later in future.