Version: Chrome 51.0.2673.0
OS: All

What steps will reproduce the problem?
(1) Apply this patch https://codereview.chromium.org/1754713005/ .
(2) Run a debug build of browser_tests with --gtest_filter='MediaRouterElementsBrowserTest.*Filter'.
(3) Observe assertion failure. See example stack trace below.

As can be seen in the code review, it is release mode that fails with this trace on trybots.  However, locally I have only been able to reproduce it in debug builds.

ASSERTION FAILED: !node.needsDistributionRecalc()
../../third_party/WebKit/Source/core/dom/shadow/FlatTreeTraversal.h(129) : static void blink::FlatTreeTraversal::assertPrecondition(const blink::Node &)
1   0x10f457942 blink::LayoutTreeBuilderTraversal::parent(blink::Node const&, blink::LayoutTreeBuilderTraversal::ParentDetails*)
2   0x10f8536c9 blink::ElementResolveContext::ElementResolveContext(blink::Element&)
3   0x10f887647 blink::StyleResolverState::StyleResolverState(blink::Document&, blink::Element*, blink::ComputedStyle const*)
4   0x10f876784 blink::StyleResolver::createAnimatableValueSnapshot(blink::Element&, blink::ComputedStyle const*, blink::CSSPropertyID, blink::CSSValue*)
5   0x10f71e5f2 blink::StringKeyframe::CSSPropertySpecificKeyframe::populateAnimatableValue(blink::CSSPropertyID, blink::Element&, blink::ComputedStyle const*, bool) const
6   0x10f702139 blink::KeyframeEffectModelBase::snapshotAllCompositorKeyframes(blink::Element&, blink::ComputedStyle const*)
7   0x10f702066 blink::KeyframeEffectModelBase::forceConversionsToAnimatableValues(blink::Element&, blink::ComputedStyle const*)
8   0x10f6f9289 blink::(anonymous namespace)::createEffectModelFromKeyframes(blink::Element&, WTF::Vector<WTF::RefPtr<blink::StringKeyframe>, 0ul, WTF::PartitionAllocator> const&, bool, blink::ExceptionState&)
9   0x10f6f8533 blink::EffectInput::convertArrayForm(blink::Element&, WTF::Vector<blink::Dictionary, 0ul, WTF::PartitionAllocator> const&, blink::ExceptionState&)
10  0x10ff0331e blink::ElementAnimation::animate(blink::ExecutionContext*, blink::Element&, blink::EffectModelOrDictionarySequenceOrDictionary const&, blink::KeyframeEffectOptions const&, blink::ExceptionState&)
11  0x10ff02196 blink::ElementV8Internal::animateMethodCallback(v8::FunctionCallbackInfo<v8::Value> const&)
12  0x10e6d2dbd v8::internal::FunctionCallbackArguments::Call(void (*)(v8::FunctionCallbackInfo<v8::Value> const&))
13  0x10e7122a8 v8::internal::MaybeHandle<v8::internal::Object> v8::internal::(anonymous namespace)::HandleApiCallHelper<false>(v8::internal::Isolate*, v8::internal::(anonymous namespace)::BuiltinArguments<(v8::internal::BuiltinExtraArguments)1>)
14  0x10e731ff6 v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*)
15  0x3429bc06187
16  0x3429c0b4436
17  0x3429c0afc7e
Received signal 11 SEGV_MAPERR 0000fbadbeef
 [0x00010cd8b30a]
 [0x7fff8e35a5aa]
 [0x2f656372756f532f]
 [0x00010f457942]
 [0x00010f8536c9]
 [0x00010f887647]
 [0x00010f876784]
 [0x00010f71e5f2]
 [0x00010f702139]
 [0x00010f702066]
 [0x00010f6f9289]
 [0x00010f6f8533]
 [0x00010ff0331e]
 [0x00010ff02196]
 [0x00010e6d2dbd]
 [0x00010e7122a8]
 [0x00010e731ff6]
 [0x03429bc06187]
 [0x03429c0b4436]
 [0x03429c0afc7e]
[end of stack trace]