Add another LookupIterator constructor, and switch to delegating constructors.

src/lookup.h

Index: src/lookup.h
diff --git a/src/lookup.h b/src/lookup.h
index ffc7904b2add60da6463943b49ca5175487b448d..736cebc0900ef9464db1affcace11d59fdfc0af8 100644
--- a/src/lookup.h
+++ b/src/lookup.h
@@ -43,30 +43,26 @@ class LookupIterator final BASE_EMBEDDED {
 
   LookupIterator(Handle<Object> receiver, Handle<Name> name,
                  Configuration configuration = DEFAULT)
-      : configuration_(ComputeConfiguration(configuration, name)),
-        interceptor_state_(InterceptorState::kUninitialized),
-        property_details_(PropertyDetails::Empty()),
-        isolate_(name->GetIsolate()),
-        name_(isolate_->factory()->InternalizeName(name)),
-        receiver_(receiver),
-        initial_holder_(GetRoot(isolate_, receiver)),
-        // kMaxUInt32 isn't a valid index.
-        index_(kMaxUInt32),
-        number_(DescriptorArray::kNotFound) {
-#ifdef DEBUG
-    uint32_t index;  // Assert that the name is not an array index.
-    DCHECK(!name->AsArrayIndex(&index));
-#endif  // DEBUG
-    Start<false>();
-  }
+      : LookupIterator(name->GetIsolate(), receiver, name, configuration) {}
+
+  LookupIterator(Isolate* isolate, Handle<Object> receiver, Handle<Name> name,
+                 Configuration configuration = DEFAULT)
+      : LookupIterator(isolate, receiver, name, GetRoot(isolate, receiver),
+                       configuration) {}
 
   LookupIterator(Handle<Object> receiver, Handle<Name> name,
                  Handle<JSReceiver> holder,
                  Configuration configuration = DEFAULT)
+      : LookupIterator(name->GetIsolate(), receiver, name, holder,
+                       configuration) {}
+
+  LookupIterator(Isolate* isolate, Handle<Object> receiver, Handle<Name> name,
+                 Handle<JSReceiver> holder,
+                 Configuration configuration = DEFAULT)
       : configuration_(ComputeConfiguration(configuration, name)),
         interceptor_state_(InterceptorState::kUninitialized),
         property_details_(PropertyDetails::Empty()),
-        isolate_(name->GetIsolate()),
+        isolate_(isolate),
         name_(isolate_->factory()->InternalizeName(name)),
         receiver_(receiver),
         initial_holder_(holder),
@@ -82,18 +78,8 @@ class LookupIterator final BASE_EMBEDDED {
 
   LookupIterator(Isolate* isolate, Handle<Object> receiver, uint32_t index,
                  Configuration configuration = DEFAULT)
-      : configuration_(configuration),
-        interceptor_state_(InterceptorState::kUninitialized),
-        property_details_(PropertyDetails::Empty()),
-        isolate_(isolate),
-        receiver_(receiver),
-        initial_holder_(GetRoot(isolate, receiver, index)),
-        index_(index),
-        number_(DescriptorArray::kNotFound) {
-    // kMaxUInt32 isn't a valid index.
-    DCHECK_NE(kMaxUInt32, index_);
-    Start<true>();
-  }
+      : LookupIterator(isolate, receiver, index,
+                       GetRoot(isolate, receiver, index), configuration) {}
 
   LookupIterator(Isolate* isolate, Handle<Object> receiver, uint32_t index,
                  Handle<JSReceiver> holder,