The Chromium Chronicle #33: View AnimationBuilder

auto primary_title_sequence = std::make_unique<LayerAnimationSequence>();
auto working_sequence = std::make_unique<LayerAnimationSequence>();
primary_title_sequence->set_is_repeating(true);
working_sequence->set_is_repeating(true);

primary_title_sequence->AddElement(CreatePauseElement(OPACITY, base::Seconds(2)));
primary_title_sequence->AddElement(CreateOpacityElement(0.0f, base::Seconds(1)));
primary_title_sequence->AddElement(CreatePauseElement(OPACITY, base::Seconds(2)));
primary_title_sequence->AddElement(CreateOpacityElement(1.0f, base::Seconds(1)));

working_sequence->AddElement(CreatePauseElement(OPACITY, base::Seconds(2)));
working_sequence->AddElement(CreateOpacityElement(1.0f, base::Seconds(1)));
working_sequence->AddElement(CreatePauseElement(OPACITY, base::Seconds(2)));
working_sequence->AddElement(CreateOpacityElement(0.0f, base::Seconds(1)));

primary_title_->layer()->GetAnimator()->StartAnimation(primary_title_sequence.release());
working_->layer()->GetAnimator()->StartAnimation(working_sequence.release());

AnimationBuilder()
    .Repeatedly()
    .Offset(base::Seconds(2))
    .SetDuration(base::Seconds(1))
    .SetOpacity(primary_title_, 0.0f)
    .SetOpacity(working_, 1.0f)
    .Offset(base::Seconds(2))
    .SetDuration(base::Seconds(1))
    .SetOpacity(primary_title_, 1.0f)
    .SetOpacity(working_, 0.0f);