Fix the blink_gc_plugin tests after crrev.com/802490

TBR=thakis

Bug: 1122969
Change-Id: Iee48f90cb68ea8088101bfdf37b432f99729af95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2380655Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802630}

tools/clang/blink_gc_plugin/tests/heap/stubs.h

@@ -271,7 +271,7 @@ template<typename T>
 class HeapListHashSet : public ListHashSet<T, void, void, HeapAllocator> { };
 
 template<typename T>
-class HeapLinkedHashSet : public LinkedHashSet<T, void, void, HeapAllocator> {
+class HeapLinkedHashSet : public LinkedHashSet<T, void, HeapAllocator> {
 };
 
 template<typename T>