Make some foo.h headers usable without foo-inl.h header.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d780119787d7976419dc8319f4f5942cc1e12f3d..afb057ffb4188e8bf0f5b4f778f562648cc4586f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1251,6 +1251,11 @@ 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); }
+
+
 struct Brief {
   explicit Brief(const Object* const v) : value(v) {}
   const Object* value;