Replace NULL with nullptr in all C++ files.

webrtc/base/socketpool.cc

Index: webrtc/base/socketpool.cc
diff --git a/webrtc/base/socketpool.cc b/webrtc/base/socketpool.cc
index f316193b6e50f53e118aaf417813faafbc467e30..b16f192c93dfb9b8710a1ca2975ea33dd7fc7eae 100644
--- a/webrtc/base/socketpool.cc
+++ b/webrtc/base/socketpool.cc
@@ -61,7 +61,7 @@ StreamInterface* StreamCache::RequestConnectedStream(
     LOG_F(LS_VERBOSE) << "Providing new stream";
     return active_.front().second;
   }
-  return NULL;
+  return nullptr;
 }
 
 void StreamCache::ReturnConnectedStream(StreamInterface* stream) {
@@ -124,13 +124,13 @@ NewSocketPool::RequestConnectedStream(const SocketAddress& remote, int* err) {
   if (!socket) {
     if (err)
       *err = -1;
-    return NULL;
+    return nullptr;
   }
   if ((socket->Connect(remote) != 0) && !socket->IsBlocking()) {
     if (err)
       *err = socket->GetError();
     delete socket;
-    return NULL;
+    return nullptr;
   }
   if (err)
     *err = 0;
@@ -147,8 +147,7 @@ NewSocketPool::ReturnConnectedStream(StreamInterface* stream) {
 //////////////////////////////////////////////////////////////////////
 
 ReuseSocketPool::ReuseSocketPool(SocketFactory* factory)
-: factory_(factory), stream_(NULL), checked_out_(false) {
-}
+    : factory_(factory), stream_(nullptr), checked_out_(false) {}
 
 ReuseSocketPool::~ReuseSocketPool() {
   RTC_DCHECK(!checked_out_);
@@ -171,7 +170,7 @@ ReuseSocketPool::RequestConnectedStream(const SocketAddress& remote, int* err) {
     if (!socket) {
       if (err)
         *err = -1;
-      return NULL;
+      return nullptr;
     }
     stream_ = new SocketStream(socket);
   }
@@ -184,7 +183,7 @@ ReuseSocketPool::RequestConnectedStream(const SocketAddress& remote, int* err) {
         && !stream_->GetSocket()->IsBlocking()) {
       if (err)
         *err = stream_->GetSocket()->GetError();
-      return NULL;
+      return nullptr;
     } else {
       LOG_F(LS_VERBOSE) << "Opening connection to: " << remote_;
     }
@@ -267,7 +266,7 @@ StreamInterface* LoggingPoolAdapter::RequestConnectedStream(
     logging->Attach(stream);
     return logging;
   }
-  return NULL;
+  return nullptr;
 }
 
 void LoggingPoolAdapter::ReturnConnectedStream(StreamInterface* stream) {