When running tests that rely on accelerated compositing, the DumpRenderTree window needs to be setAutodisplay:YES, otherwise the underlying engine does not start accelerated animations correctly.
Created attachment 27499 [details]
Comment on attachment 27499 [details]
In pointers to Objective-C instances, the space should go before the * (including in static_cast<>s). I am not sure why you are checking that the WebView responds to _isUsingAcceleratedCompositing. DumpRenderTree is not expected to be used with old WebKit.
You don't need to declare and initialize the firstView variable outside the if statement.