[cctest] Fix invalid assumption in test-unboxed-doubles

test/cctest/test-unboxed-doubles.cc

Index: test/cctest/test-unboxed-doubles.cc
diff --git a/test/cctest/test-unboxed-doubles.cc b/test/cctest/test-unboxed-doubles.cc
index 52d045565229b69a5ff8327fbb6ae091b96f44b3..35b1b4cf7991784f8045ee01afbd5249e629c8de 100644
--- a/test/cctest/test-unboxed-doubles.cc
+++ b/test/cctest/test-unboxed-doubles.cc
@@ -1411,7 +1411,7 @@ static void TestWriteBarrier(Handle<Map> map, Handle<Map> new_map,
     obj = factory->NewJSObjectFromMap(map, TENURED);
     CHECK(old_space->Contains(*obj));
 
-    obj_value = factory->NewJSArray(32 * KB, FAST_HOLEY_ELEMENTS);

[jgruber, 2017/03/16 15:57:13]

I don't think the capacity of 32*KB was significant for this test, but please
double-check.

+    obj_value = factory->NewJSArray(0, FAST_HOLEY_ELEMENTS);

[jgruber, 2017/03/16 15:57:13]

Requesting an empty array omits allocation of elements, therefore the CHECK
below holds.

   }
 
   CHECK(heap->InNewSpace(*obj_value));