Introduce --zap-cpp-pointers (off by default)

src/api-arguments.h

 // Copyright 2016 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_API_ARGUMENTS_H_
 #define V8_API_ARGUMENTS_H_
 
 #include "src/api.h"
 #include "src/isolate.h"
 #include "src/visitors.h"
 
 namespace v8 {
 namespace internal {
 
 // Custom arguments replicate a small segment of stack that can be
 // accessed through an Arguments object the same way the actual stack
 // can.
 template <int kArrayLength>
 class CustomArgumentsBase : public Relocatable {
  public:
-  virtual inline void IterateInstance(RootVisitor* v) {
+  inline void IterateInstance(RootVisitor* v) override {
     v->VisitRootPointers(Root::kRelocatable, values_, values_ + kArrayLength);
   }
 
  protected:
   inline Object** begin() { return values_; }
   explicit inline CustomArgumentsBase(Isolate* isolate)
       : Relocatable(isolate) {}
   Object* values_[kArrayLength];
 };
 
@@ skipping 160 matching lines @@
 
  private:
   internal::Object** argv_;
   int argc_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_API_ARGUMENTS_H_