Simplify Object::IsHeapObject() into !IsSmi()

Change-Id: I10ca732853729564c59755648d5fb369fb49ce97
Reviewed-on: https://chromium-review.googlesource.com/446364Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43442}

src/objects.h

@@ -1522,8 +1522,10 @@ class Object {
 
 // In objects.h to be usable without objects-inl.h inclusion.
 bool Object::IsSmi() const { return HAS_SMI_TAG(this); }
-bool Object::IsHeapObject() const { return Internals::HasHeapObjectTag(this); }
-
+bool Object::IsHeapObject() const {
+  DCHECK_EQ(!IsSmi(), Internals::HasHeapObjectTag(this));
+  return !IsSmi();
+}
 
 struct Brief {
   explicit Brief(const Object* const v) : value(v) {}