[stubs] Introduce ToIntegerStub and unify the handling of %_ToInteger.

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index df3b1dd5030124a88be2e5116375a12004bcaba7..fbfdd5f644c1b921973b7472b28c66e3393d8f2d 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -173,6 +173,12 @@ Callable CodeFactory::ToName(Isolate* isolate) {
 
 
 // static
+Callable CodeFactory::ToInteger(Isolate* isolate) {
+  ToIntegerStub stub(isolate);
+  return Callable(stub.GetCode(), stub.GetCallInterfaceDescriptor());
+}
+
+// static
 Callable CodeFactory::ToLength(Isolate* isolate) {
   ToLengthStub stub(isolate);
   return Callable(stub.GetCode(), stub.GetCallInterfaceDescriptor());