Fix CreateFillerObjectAt() call for 64b platforms

This patch fixes build error for 64bit platforms introduces in
https://codereview.chromium.org/2793323002
Error message from MIPS64 buildbot: error: implicit conversion loses
integer precision: 'long' to 'int' [-Werror,-Wshorten-64-to-32]

BUG=

Review-Url: https://codereview.chromium.org/2801713004
Cr-Commit-Position: refs/heads/master@{#44460}

src/heap/mark-compact.cc

@@ -257,8 +257,9 @@ void EvacuationVerifier::VerifyEvacuation(PagedSpace* space) {
   for (Page* p : *space) {
     if (p->IsEvacuationCandidate()) continue;
     if (p->Contains(space->top()))
-      heap_->CreateFillerObjectAt(space->top(), space->limit() - space->top(),
-                                  ClearRecordedSlots::kNo);
+      heap_->CreateFillerObjectAt(
+          space->top(), static_cast<int>(space->limit() - space->top()),
+          ClearRecordedSlots::kNo);
 
     VerifyEvacuationOnPage(p->area_start(), p->area_end());
   }