1. Build release-with-dcheck version of content_shell;
2. run-webkit-tests paint/invalidation/svg/image-animation-with-zoom.html --child-processes=1 --iterations=100

Actual: sometimes the test may crash one or more times.

Crash stack:

crash log for renderer (pid <unknown>):
STDERR: [1:1:1211/144040.215564:FATAL:IdleSpellCheckCallback.cpp(171)] Check failed: GetFrame().GetDocument()->IsActive(). 
STDERR: #0 0x00000307fe4c base::debug::StackTrace::StackTrace()
STDERR: #1 0x00000309e51c logging::LogMessage::~LogMessage()
STDERR: #2 0x000005041438 blink::IdleSpellCheckCallback::invoke()
STDERR: #3 0x000004f0faaf blink::ScriptedIdleTaskController::RunCallback()
STDERR: #4 0x000004f0f238 blink::internal::IdleRequestCallbackWrapper::IdleTaskFired()
STDERR: #5 0x000004f114e0 _ZN4base8internal7InvokerINS0_9BindStateIPFv13scoped_refptrIN5blink8internal26IdleRequestCallbackWrapperEEEJS7_EEEFvvEE7RunOnceEPNS0_13BindStateBaseE
STDERR: #6 0x0000026e25d0 WTF::ThreadCheckingCallbackWrapper<>::Run()
STDERR: #7 0x0000027709c4 blink::scheduler::WebSchedulerImpl::RunIdleTask()

I guess !GetFrame().GetDocument()->IsActive() is a valid (though rare) situation that should be handled instead of DCHECK?