[turbofan] Add new StringFromCharCode simplified operator.

src/compiler/effect-control-linearizer.h

Index: src/compiler/effect-control-linearizer.h
diff --git a/src/compiler/effect-control-linearizer.h b/src/compiler/effect-control-linearizer.h
index 9e666b6e2c4d37ae8d7fcce06b3c8af53c8c92a6..083e345f70aae58e7430c14de012769ca1ddc592 100644
--- a/src/compiler/effect-control-linearizer.h
+++ b/src/compiler/effect-control-linearizer.h
@@ -77,6 +77,8 @@ class EffectControlLinearizer {
                                          Node* control);
   ValueEffectControl LowerObjectIsUndetectable(Node* node, Node* effect,
                                                Node* control);
+  ValueEffectControl LowerStringFromCharCode(Node* node, Node* effect,
+                                             Node* control);
   ValueEffectControl AllocateHeapNumberWithValue(Node* node, Node* effect,
                                                  Node* control);
 
@@ -90,6 +92,8 @@ class EffectControlLinearizer {
   Node* SmiMaxValueConstant();
   Node* SmiShiftBitsConstant();
 
+  Factory* factory() const;
+  Isolate* isolate() const;
   JSGraph* jsgraph() const { return js_graph_; }
   Graph* graph() const;
   Schedule* schedule() const { return schedule_; }