Introduce exception object and remove some uses of MaybeObject::IsFailure().

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 023caa5ddf93f7a2fdf595121a0581553a23440f..179def457e474a35a4b369ae85a97b4891a27a92 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1000,6 +1000,11 @@ bool Object::IsTheHole() {
 }
 
 
+bool Object::IsException() {
+  return IsOddball() && Oddball::cast(this)->kind() == Oddball::kException;
+}
+
+
 bool Object::IsUninitialized() {
   return IsOddball() && Oddball::cast(this)->kind() == Oddball::kUninitialized;
 }
@@ -1046,20 +1051,6 @@ Handle<Object> Object::ToSmi(Isolate* isolate, Handle<Object> object) {
 }
 
 
-// TODO(ishell): Use handlified version instead.
-MaybeObject* Object::ToSmi() {
-  if (IsSmi()) return this;
-  if (IsHeapNumber()) {
-    double value = HeapNumber::cast(this)->value();
-    int int_value = FastD2I(value);
-    if (value == FastI2D(int_value) && Smi::IsValid(int_value)) {
-      return Smi::FromInt(int_value);
-    }
-  }
-  return Failure::Exception();
-}
-
-
 MaybeHandle<JSReceiver> Object::ToObject(Isolate* isolate,
                                          Handle<Object> object) {
   return ToObject(