[turbofan] Build s/NULL/nullptr/g and CHECK(x != nullptr) to CHECK_NOT_NULL(x).

src/compiler/ast-loop-assignment-analyzer.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_AST_LOOP_ASSIGNMENT_ANALYZER_H_
 #define V8_COMPILER_AST_LOOP_ASSIGNMENT_ANALYZER_H_
 
 #include "src/ast/ast.h"
 #include "src/bit-vector.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 
 class Variable;
 class Scope;
 
 namespace compiler {
 
 // The result of analyzing loop assignments.
 class LoopAssignmentAnalysis : public ZoneObject {
  public:
   BitVector* GetVariablesAssignedInLoop(IterationStatement* loop) {
     for (size_t i = 0; i < list_.size(); i++) {
       // TODO(turbofan): hashmap or binary search for loop assignments.
       if (list_[i].first == loop) return list_[i].second;
     }
     UNREACHABLE();  // should never ask for loops that aren't here!
-    return NULL;
+    return nullptr;
   }
 
   int GetAssignmentCountForTesting(Scope* scope, Variable* var);
 
  private:
   friend class AstLoopAssignmentAnalyzer;
   explicit LoopAssignmentAnalysis(Zone* zone) : list_(zone) {}
   ZoneVector<std::pair<IterationStatement*, BitVector*>> list_;
 };
 
@@ skipping 16 matching lines @@
   Zone* zone_;
   ZoneDeque<BitVector*> loop_stack_;
   LoopAssignmentAnalysis* result_;
 
   CompilationInfo* info() { return info_; }
 
   void Enter(IterationStatement* loop);
   void Exit(IterationStatement* loop);
 
   void VisitIfNotNull(AstNode* node) {
-    if (node != NULL) Visit(node);
+    if (node != nullptr) Visit(node);
   }
 
   void AnalyzeAssignment(Variable* var);
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
   DISALLOW_COPY_AND_ASSIGN(AstLoopAssignmentAnalyzer);
 };
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_AST_LOOP_ASSIGNMENT_ANALYZER_H_