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

src/compiler/interpreter-assembler.cc

Index: src/compiler/interpreter-assembler.cc
diff --git a/src/compiler/interpreter-assembler.cc b/src/compiler/interpreter-assembler.cc
index d6ca45fc54f5a0e9cc7538fdc6644c9da9308fc1..54add6196040629b66a1cc8fb08713c96072bf7a 100644
--- a/src/compiler/interpreter-assembler.cc
+++ b/src/compiler/interpreter-assembler.cc
@@ -169,7 +169,7 @@ Node* InterpreterAssembler::NumberConstant(double value) {
 }
 
 
-Node* InterpreterAssembler::HeapConstant(Unique<HeapObject> object) {
+Node* InterpreterAssembler::HeapConstant(Handle<HeapObject> object) {
   return raw_assembler_->HeapConstant(object);
 }
 
@@ -241,8 +241,7 @@ Node* InterpreterAssembler::CallJSBuiltin(int context_index, Node* receiver,
 
 void InterpreterAssembler::Return() {
   Node* exit_trampoline_code_object =
-      HeapConstant(Unique<HeapObject>::CreateImmovable(
-          isolate()->builtins()->InterpreterExitTrampoline()));
+      HeapConstant(isolate()->builtins()->InterpreterExitTrampoline());
   // If the order of the parameters you need to change the call signature below.
   STATIC_ASSERT(0 == Linkage::kInterpreterAccumulatorParameter);
   STATIC_ASSERT(1 == Linkage::kInterpreterRegisterFileParameter);