[cleanup] Replace 0 and NULL with nullptr for external includes.

Fixing clang-tidy warning.

Bug: v8:8015
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I4f9eb0fedbe1d35a571f3d5b111705a820edfb5b
Reviewed-on: https://chromium-review.googlesource.com/1224377
Commit-Queue: Florian Sattler <sattlerf@google.com>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55905}

include/v8-profiler.h

@@ -800,8 +800,8 @@ class V8_EXPORT HeapProfiler {
    * Takes a heap snapshot and returns it.
    */
   const HeapSnapshot* TakeHeapSnapshot(
-      ActivityControl* control = NULL,
-      ObjectNameResolver* global_object_name_resolver = NULL);
+      ActivityControl* control = nullptr,
+      ObjectNameResolver* global_object_name_resolver = nullptr);
 
   /**
    * Starts tracking of heap objects population statistics. After calling
@@ -828,7 +828,7 @@ class V8_EXPORT HeapProfiler {
    * method.
    */
   SnapshotObjectId GetHeapStats(OutputStream* stream,
-                                int64_t* timestamp_us = NULL);
+                                int64_t* timestamp_us = nullptr);
 
   /**
    * Stops tracking of heap objects population statistics, cleans up all

include/v8-util.h

@@ -94,11 +94,11 @@ class DefaultPersistentValueMapTraits : public StdMapTraits<K, V> {
 
   static WeakCallbackDataType* WeakCallbackParameter(
       MapType* map, const K& key, Local<V> value) {
-    return NULL;
+    return nullptr;
   }
   static MapType* MapFromWeakCallbackInfo(
       const WeakCallbackInfo<WeakCallbackDataType>& data) {
-    return NULL;
+    return nullptr;
   }
   static K KeyFromWeakCallbackInfo(
       const WeakCallbackInfo<WeakCallbackDataType>& data) {
@@ -302,7 +302,7 @@ class PersistentValueMapBase {
 
   static PersistentContainerValue ClearAndLeak(Global<V>* persistent) {
     V* v = persistent->val_;
-    persistent->val_ = 0;
+    persistent->val_ = nullptr;
     return reinterpret_cast<PersistentContainerValue>(v);
   }
 
@@ -633,7 +633,7 @@ class PersistentValueVector {
  private:
   static PersistentContainerValue ClearAndLeak(Global<V>* persistent) {
     V* v = persistent->val_;
-    persistent->val_ = 0;
+    persistent->val_ = nullptr;
     return reinterpret_cast<PersistentContainerValue>(v);
   }