[turbofan] Introduce CheckIf simplified operator.

src/compiler/simplified-operator-reducer.h

Index: src/compiler/simplified-operator-reducer.h
diff --git a/src/compiler/simplified-operator-reducer.h b/src/compiler/simplified-operator-reducer.h
index e42561de022090fae6abafc0b39e0d2868a5af39..44bfdff3e3d246a8a48fe4b3b6bc198e1290dd4b 100644
--- a/src/compiler/simplified-operator-reducer.h
+++ b/src/compiler/simplified-operator-reducer.h
@@ -9,6 +9,11 @@
 
 namespace v8 {
 namespace internal {
+
+// Forward declarations.
+class Factory;
+class Isolate;
+
 namespace compiler {
 
 // Forward declarations.
@@ -36,7 +41,9 @@ class SimplifiedOperatorReducer final : public AdvancedReducer {
   Reduction ReplaceNumber(double value);
   Reduction ReplaceNumber(int32_t value);
 
+  Factory* factory() const;
   Graph* graph() const;
+  Isolate* isolate() const;
   JSGraph* jsgraph() const { return jsgraph_; }
   MachineOperatorBuilder* machine() const;
   SimplifiedOperatorBuilder* simplified() const;