[ElementTiming] Remove a DCHECK for cached image

Bug: 896024
Change-Id: Ie4a0ba6a07c96557f0bfd464e523c0ad8d804c8e
Reviewed-on: https://chromium-review.googlesource.com/c/1336431Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608267}

third_party/blink/renderer/core/paint/image_element_timing.cc

@@ -57,7 +57,9 @@ void ImageElementTiming::NotifyImagePainted(const HTMLImageElement* element,
     return;
 
   // Skip the computations below if the element is not same origin.
-  DCHECK(layout_image->CachedImage());
+  if (!layout_image->CachedImage())
+    return;
+
   const KURL& url = layout_image->CachedImage()->Url();
   DCHECK(GetSupplementable()->document() == &layout_image->GetDocument());
   if (!SecurityOrigin::AreSameSchemeHostPort(layout_image->GetDocument().Url(),