Fix compilation failure due to overload of virtual function

test/mkgrokdump/mkgrokdump.cc

Index: test/mkgrokdump/mkgrokdump.cc
diff --git a/test/mkgrokdump/mkgrokdump.cc b/test/mkgrokdump/mkgrokdump.cc
index e5a41a13ba3a7ce09b175c28ada3066a0752126a..ab6247fa6b69d8ddba2b0cb088bd6ea50155dcb8 100644
--- a/test/mkgrokdump/mkgrokdump.cc
+++ b/test/mkgrokdump/mkgrokdump.cc
@@ -37,7 +37,11 @@ class MockArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
  public:
   void* Allocate(size_t length) override { return nullptr; }
   void* AllocateUninitialized(size_t length) override { return nullptr; }
+  void* Reserve(size_t length) override { return nullptr; }
+  void Free(void* data, size_t length, AllocationMode mode) override {}
   void Free(void* p, size_t) override {}
+  void SetProtection(void* data, size_t length,
+                     Protection protection) override {}
 };
 
 static int DumpHeapConstants(const char* argv0) {