Access double fields in C++ as uint64_t fields to preserve signaling bit of a NaN.

test/cctest/heap/test-alloc.cc

Index: test/cctest/heap/test-alloc.cc
diff --git a/test/cctest/heap/test-alloc.cc b/test/cctest/heap/test-alloc.cc
index 3485c0ab07f03264332fd8b68046f818fc0fa2d6..27070c9da835661988532ce6bfc7af549c9a08d1 100644
--- a/test/cctest/heap/test-alloc.cc
+++ b/test/cctest/heap/test-alloc.cc
@@ -48,7 +48,7 @@ AllocationResult v8::internal::HeapTester::AllocateAfterFailures() {
   // Make sure we can allocate through optimized allocation functions
   // for specific kinds.
   heap->AllocateFixedArray(100).ToObjectChecked();
-  heap->AllocateHeapNumber(0.42).ToObjectChecked();
+  heap->AllocateHeapNumber().ToObjectChecked();
   Object* object = heap->AllocateJSObject(
       *CcTest::i_isolate()->object_function()).ToObjectChecked();
   heap->CopyJSObject(JSObject::cast(object)).ToObjectChecked();