Remove outdated DCHECK in SVGUseElement::InsertedInto

This DCHECK was made obsolete by
9b88406d, since it stopped using the
"pending resource" flag for <use>.

Bug: 825460
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ie1202097eb2172ef9ed3866e3a6575fbe4aa09db
Reviewed-on: https://chromium-review.googlesource.com/980252Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#545854}

third_party/WebKit/Source/core/svg/SVGUseElement.cpp

@@ -121,7 +121,6 @@ Node::InsertionNotificationRequest SVGUseElement::InsertedInto(
     return kInsertionDone;
 #if DCHECK_IS_ON()
   DCHECK(!target_element_instance_ || !IsWellFormedDocument(&GetDocument()));
-  DCHECK(!HasPendingResources() || !IsWellFormedDocument(&GetDocument()));
 #endif
   InvalidateShadowTree();
   return kInsertionDone;