Mark JSArrayBuffer::SetupAllocatingData with WARN_UNUSED_RESULT.

test/cctest/heap/test-page-promotion.cc

Index: test/cctest/heap/test-page-promotion.cc
diff --git a/test/cctest/heap/test-page-promotion.cc b/test/cctest/heap/test-page-promotion.cc
index 3207c262503c1dc031defd8938008486c53501ef..4b08514e527a3af5a8f53f99b6e7df990657f4e1 100644
--- a/test/cctest/heap/test-page-promotion.cc
+++ b/test/cctest/heap/test-page-promotion.cc
@@ -115,7 +115,7 @@ UNINITIALIZED_TEST(PagePromotion_NewToNewJSArrayBuffer) {
     // Allocate a buffer we would like to check against.
     Handle<JSArrayBuffer> buffer =
         i_isolate->factory()->NewJSArrayBuffer(SharedFlag::kNotShared);
-    JSArrayBuffer::SetupAllocatingData(buffer, i_isolate, 100);
+    CHECK(JSArrayBuffer::SetupAllocatingData(buffer, i_isolate, 100));
     std::vector<Handle<FixedArray>> handles;
     // Simulate a full space, filling the interesting page with live objects.
     heap::SimulateFullSpace(heap->new_space(), &handles);