Clean up ObserverList Pointers to use nullptr instad of NULL or 0

We expect the type to be ObserverType*, so let's use nullptr.

Review URL: https://codereview.chromium.org/1101103002

Cr-Commit-Position: refs/heads/master@{#326679}

base/observer_list.h

@@ -143,13 +143,13 @@ ObserverListBase<ObserverType>::Iterator::~Iterator() {
 template <class ObserverType>
 ObserverType* ObserverListBase<ObserverType>::Iterator::GetNext() {
   if (!list_.get())
-    return NULL;
+    return nullptr;
   ListType& observers = list_->observers_;
   // Advance if the current element is null
   size_t max_index = std::min(max_index_, observers.size());
   while (index_ < max_index && !observers[index_])
     ++index_;
-  return index_ < max_index ? observers[index_++] : NULL;
+  return index_ < max_index ? observers[index_++] : nullptr;
 }
 
 template <class ObserverType>
@@ -170,7 +170,7 @@ void ObserverListBase<ObserverType>::RemoveObserver(ObserverType* obs) {
     std::find(observers_.begin(), observers_.end(), obs);
   if (it != observers_.end()) {
     if (notify_depth_) {
-      *it = 0;
+      *it = nullptr;
     } else {
       observers_.erase(it);
     }
@@ -192,7 +192,7 @@ void ObserverListBase<ObserverType>::Clear() {
   if (notify_depth_) {
     for (typename ListType::iterator it = observers_.begin();
       it != observers_.end(); ++it) {
-      *it = 0;
+      *it = nullptr;
     }
   } else {
     observers_.clear();
@@ -202,8 +202,8 @@ void ObserverListBase<ObserverType>::Clear() {
 template <class ObserverType>
 void ObserverListBase<ObserverType>::Compact() {
   observers_.erase(
-      std::remove(observers_.begin(), observers_.end(),
-                  static_cast<ObserverType*>(NULL)), observers_.end());
+      std::remove(observers_.begin(), observers_.end(), nullptr),
+      observers_.end());
 }
 
 template <class ObserverType, bool check_empty = false>
@@ -235,7 +235,7 @@ class ObserverList : public ObserverListBase<ObserverType> {
       ObserverListBase<ObserverType>::Iterator it_inside_observer_macro( \
           &observer_list);                                               \
       ObserverType* obs;                                                 \
-      while ((obs = it_inside_observer_macro.GetNext()) != NULL)         \
+      while ((obs = it_inside_observer_macro.GetNext()) != nullptr)         \
         obs->func;                                                       \
     }                                                                    \
   } while (0)

base/observer_list_threadsafe.h

@@ -111,7 +111,7 @@ class ObserverListThreadSafe
     if (!base::MessageLoop::current())
       return;
 
-    ObserverList<ObserverType>* list = NULL;
+    ObserverList<ObserverType>* list = nullptr;
     base::PlatformThreadId thread_id = base::PlatformThread::CurrentId();
     {
       base::AutoLock lock(list_lock_);
@@ -128,8 +128,8 @@ class ObserverListThreadSafe
   // If the observer to be removed is in the list, RemoveObserver MUST
   // be called from the same thread which called AddObserver.
   void RemoveObserver(ObserverType* obs) {
-    ObserverListContext* context = NULL;
-    ObserverList<ObserverType>* list = NULL;
+    ObserverListContext* context = nullptr;
+    ObserverList<ObserverType>* list = nullptr;
     base::PlatformThreadId thread_id = base::PlatformThread::CurrentId();
     {
       base::AutoLock lock(list_lock_);
@@ -230,7 +230,7 @@ class ObserverListThreadSafe
     {
       typename ObserverList<ObserverType>::Iterator it(&context->list);
       ObserverType* obs;
-      while ((obs = it.GetNext()) != NULL)
+      while ((obs = it.GetNext()) != nullptr)
         method.Run(obs);
     }
 

base/observer_list_unittest.cc

@@ -94,7 +94,7 @@ class AddRemoveThread : public PlatformThread::Delegate,
  public:
   AddRemoveThread(ObserverListThreadSafe<Foo>* list, bool notify)
       : list_(list),
-        loop_(NULL),
+        loop_(nullptr),
         in_list_(false),
         start_(Time::Now()),
         count_observes_(0),