Bug 1349808 - Add telemetry for cases when we can't run async animations due to layer size being too large. data-review=bsmedberg, r=birtles,botond,bsmedberg

MozReview-Commit-ID: 61DBw1DHbQA

dom/animation/KeyframeEffect.cpp

@@ -129,6 +129,11 @@ KeyframeEffect::SetTarget(const Nullable<ElementOrCSSPseudoElement>& aTarget)
     // New target is null, so fall back to distribute spacing.
     KeyframeUtils::ApplyDistributeSpacing(mKeyframes);
   }
+
+  // If the new target frame is also oversized we should probably record that
+  // too so we have a more complete picture of the type of frame sizes we
+  // encounter, hence we reset the telemetry flag here.
+  mRecordedContentTooLarge = false;
 }
 
 void