[turbofan] Remove usage of Unique<T> from graph.

src/compiler/raw-machine-assembler.h

Index: src/compiler/raw-machine-assembler.h
diff --git a/src/compiler/raw-machine-assembler.h b/src/compiler/raw-machine-assembler.h
index c58db112ea9b355aa1fb7803b10a375d77c8acac..994f0d9f09265be59ef49e8b256b89ebeb351dda 100644
--- a/src/compiler/raw-machine-assembler.h
+++ b/src/compiler/raw-machine-assembler.h
@@ -72,9 +72,8 @@ class RawMachineAssembler {
   // hence will not switch the current basic block.
 
   Node* UndefinedConstant() {
-    Unique<HeapObject> unique = Unique<HeapObject>::CreateImmovable(
-        isolate()->factory()->undefined_value());
-    return NewNode(common()->HeapConstant(unique));
+    Handle<HeapObject> undefined = isolate()->factory()->undefined_value();
+    return NewNode(common()->HeapConstant(undefined));
   }
 
   // Constants.
@@ -102,10 +101,6 @@ class RawMachineAssembler {
     return NewNode(common()->Float64Constant(value));
   }
   Node* HeapConstant(Handle<HeapObject> object) {
-    Unique<HeapObject> val = Unique<HeapObject>::CreateUninitialized(object);
-    return NewNode(common()->HeapConstant(val));
-  }
-  Node* HeapConstant(Unique<HeapObject> object) {
     return NewNode(common()->HeapConstant(object));
   }
   Node* ExternalConstant(ExternalReference address) {