###!!! ASSERTION: Second ancestor is not BODY: 'contentTag == nsHTMLAtoms::body', file /Users/admin/trunk/mozilla/layout/generic/nsHTMLReflowState.cpp, line 1548

This still happens on trunk. See also bug 384504, "ASSERTION: First ancestor is not HTML".

This assertion is in CalcQuirkContainingBlockHeight, which we call because there's a percent height and we're in quirks mode. We're basically asserting that the two frames directly below the canvas will have content with HTML and Body tags, respectively. In this case, that assumption is false -- the second frame has a **Head** tag, (not Body), because the head has been told (via CSS) to be displayed. So, it looks like this assertion's assumption is too strong. We may be able to just ease up on what we're asserting, or leave the condition the same but change the assertion to a warning.

Still happens on trunk.

Still hits to this day :) ASSERTION: Second ancestor is not BODY: 'frameContent->IsHTMLElement(nsGkAtoms::body)', file layout/generic/ReflowInput.cpp, line 2078 #01: mozilla::ReflowInput::ComputeContainingBlockRectangle [layout/generic/ReflowInput.cpp:2155] #02: mozilla::ReflowInput::InitConstraints [layout/generic/ReflowInput.cpp:2263] #03: mozilla::ReflowInput::Init [layout/generic/ReflowInput.cpp:427] #04: nsBlockReflowContext::ComputeCollapsedBStartMargin [layout/generic/nsBlockReflowContext.cpp:171] #05: nsBlockFrame::ReflowBlockFrame [layout/generic/nsBlockFrame.cpp:3367] #06: nsBlockFrame::ReflowLine [layout/generic/nsBlockFrame.cpp:2870] #07: nsBlockFrame::ReflowDirtyLines [layout/generic/nsBlockFrame.cpp:2409] #08: nsBlockFrame::Reflow [layout/generic/nsBlockFrame.cpp:1248] #09: nsContainerFrame::ReflowChild [layout/generic/nsContainerFrame.cpp:937] #10: nsCanvasFrame::Reflow [layout/generic/nsCanvasFrame.cpp:756] #11: nsContainerFrame::ReflowChild [layout/generic/nsContainerFrame.cpp:937] #12: nsHTMLScrollFrame::ReflowScrolledFrame [layout/generic/nsGfxScrollFrame.cpp:554] #13: nsHTMLScrollFrame::ReflowContents [layout/generic/nsGfxScrollFrame.cpp:684] #14: nsHTMLScrollFrame::Reflow [layout/generic/nsGfxScrollFrame.cpp:1041] #15: nsContainerFrame::ReflowChild [layout/generic/nsContainerFrame.cpp:980] #16: mozilla::ViewportFrame::Reflow [layout/generic/ViewportFrame.cpp:332] #17: mozilla::PresShell::DoReflow [layout/generic/ReflowOutput.h:282] #18: mozilla::PresShell::ProcessReflowCommands [layout/base/PresShell.cpp:9121] #19: mozilla::PresShell::DoFlushPendingNotifications [layout/base/PresShell.cpp:4183] #20: mozilla::PresShell::DoFlushPendingNotifications [layout/base/PresShell.cpp:4019] #21: nsDocumentViewer::LoadComplete [layout/base/nsIPresShell.h:557] #22: nsDocShell::EndPageLoad [docshell/base/nsDocShell.cpp:7761] #23: nsDocShell::OnStateChange [docshell/base/nsDocShell.cpp:7557] #24: nsDocLoader::DoFireOnStateChange [uriloader/base/nsDocLoader.cpp:1320] #25: nsDocLoader::doStopDocumentLoad [uriloader/base/nsDocLoader.cpp:860] #26: nsDocLoader::DocLoaderIsEmpty [uriloader/base/nsDocLoader.cpp:752] #27: nsDocLoader::OnStopRequest [uriloader/base/nsDocLoader.cpp:625] #28: mozilla::net::nsLoadGroup::RemoveRequest [netwerk/base/nsLoadGroup.cpp:631] #29: nsDocument::DoUnblockOnload [dom/base/nsDocument.cpp:9364] #30: nsDocument::UnblockOnload [dom/base/nsDocument.cpp:9288] #31: nsDocument::DispatchContentLoadedEvents [dom/base/nsDocument.cpp:5575] #32: mozilla::detail::RunnableMethodImpl<nsDocument*, void (nsDocument::*)(), true, (mozilla::RunnableKind)0u>::Run [xpcom/threads/nsThreadUtils.h:1196] #33: mozilla::SchedulerGroup::Runnable::Run [xpcom/threads/SchedulerGroup.cpp:396] #34: nsThread::ProcessNextEvent [mfbt/Maybe.h:445] #35: NS_ProcessNextEvent [xpcom/threads/nsThreadUtils.cpp:524] #36: mozilla::ipc::MessagePump::Run [ipc/glue/MessagePump.cpp:98] #37: MessageLoop::RunInternal [ipc/chromium/src/base/message_loop.cc:327] #38: MessageLoop::Run [ipc/chromium/src/base/message_loop.cc:298] #39: nsBaseAppShell::Run [widget/nsBaseAppShell.cpp:160] #40: XRE_RunAppShell [toolkit/xre/nsEmbedFunctions.cpp:834] #41: mozilla::ipc::MessagePumpForChildProcess::Run [ipc/glue/MessagePump.cpp:269] #42: MessageLoop::RunInternal [ipc/chromium/src/base/message_loop.cc:327] #43: MessageLoop::Run [ipc/chromium/src/base/message_loop.cc:298] #44: XRE_InitChildProcess [toolkit/xre/nsEmbedFunctions.cpp:707] #45: content_process_main [ipc/contentproc/plugin-container.cpp:65] #46: main [browser/app/nsBrowserApp.cpp:283] #47: libc.so.6 + 0x20830 #48: _start