[turbofan] Run everything after representation selection concurrently.

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index 177cacb63c621e389917941d09fc9c71407fae2f..65858438227cdd54413b023f4309ff6d1607aa12 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -516,8 +516,10 @@ SIMD128_TYPES(SIMD128_ALLOC)
 
 // static
 Callable CodeFactory::Allocate(Isolate* isolate, PretenureFlag pretenure_flag) {
-  AllocateStub stub(isolate, pretenure_flag);
-  return Callable(stub.GetCode(), stub.GetCallInterfaceDescriptor());
+  return Callable(pretenure_flag == NOT_TENURED
+                      ? isolate->builtins()->AllocateInNewSpace()
+                      : isolate->builtins()->AllocateInOldSpace(),
+                  AllocateDescriptor(isolate));
 }
 
 // static