Bug 1587713 - Avoid layerizing very large blobs due to animated transforms. r=jrmuizel

When blobs were lazily rasterized it was relatively cheap to create very large blob layers. Now that we move to pre-rasetrizing all blob tiles during scene building, large blob layers cause excessive memory allocation and CPU usage.

Differential Revision: https://phabricator.services.mozilla.com/D51576

--HG--
extra : moz-landing-system : lando

layout/painting/nsDisplayList.cpp

@@ -8502,14 +8502,6 @@ auto nsDisplayTransform::ShouldPrerenderTransformedContent(
     return FullPrerender;
   }
 
-  // If painting is for WebRender, allow full prerender even for large size
-  // frame. With WebRender, memory usage increase for async animation is limited
-  // compared to non-WebRender case.
-  if (aBuilder->IsPaintingForWebRender()) {
-    *aDirtyRect = overflow;
-    return FullPrerender;
-  }
-
   float viewportRatioX =
       StaticPrefs::layout_animation_prerender_viewport_ratio_limit_x();
   float viewportRatioY =