Bug 1479173 - Rename LayerAnimationInto::mLayerType to LayerAnimationInfo::mDisplayitemType. r=birtles

In the case of WebRender there is no layers, but actually we'd been using it for
WebRender too, that's confusing.

Depends on D10689

Differential Revision: https://phabricator.services.mozilla.com/D10690

dom/animation/KeyframeEffect.cpp

@@ -1264,7 +1264,7 @@ KeyframeEffect::CanThrottle() const
     // Note that AnimationInfo::GetGenarationFromFrame() is supposed to work
     // with the primary frame instead of the style frame.
     Maybe<uint64_t> generation = layers::AnimationInfo::GetGenerationFromFrame(
-        GetPrimaryFrame(), record.mLayerType);
+        GetPrimaryFrame(), record.mDisplayItemType);
     // Unthrottle if the animation needs to be brought up to date
     if (!generation || effectSet->GetAnimationGeneration() != *generation) {
       return false;