Replace NULL with nullptr in all C++ files.

webrtc/base/autodetectproxy.cc

Index: webrtc/base/autodetectproxy.cc
diff --git a/webrtc/base/autodetectproxy.cc b/webrtc/base/autodetectproxy.cc
index 0ec6ecc3d4ffb75a7d37b8af64db8ff509a5a315..c482246c6934701e4d7ee84c61c9225acfe38ec3 100644
--- a/webrtc/base/autodetectproxy.cc
+++ b/webrtc/base/autodetectproxy.cc
@@ -30,8 +30,7 @@ static void SaveStringToStack(char *dst,
 }
 
 AutoDetectProxy::AutoDetectProxy(const std::string& user_agent)
-    : agent_(user_agent), resolver_(NULL), socket_(NULL), next_(0) {
-}
+    : agent_(user_agent), resolver_(nullptr), socket_(nullptr), next_(0) {}
 
 bool AutoDetectProxy::GetProxyForUrl(const char* agent,
                                      const char* url,
@@ -144,7 +143,7 @@ void AutoDetectProxy::OnResolveResult(AsyncResolverInterface* resolver) {
   } else {
     LOG(LS_INFO) << "Failed to resolve " << resolver_->address();
     resolver_->Destroy(false);
-    resolver_ = NULL;
+    resolver_ = nullptr;
     proxy_.address = SocketAddress();
     Thread::Current()->Post(RTC_FROM_HERE, this, MSG_UNRESOLVABLE);
   }
@@ -164,7 +163,7 @@ void AutoDetectProxy::Next() {
     Thread::Current()->Clear(this, MSG_UNRESOLVABLE);
     socket_->Close();
     Thread::Current()->Dispose(socket_);
-    socket_ = NULL;
+    socket_ = nullptr;
   }
   int timeout = 2000;
   if (proxy_.address.IsUnresolvedIP()) {
@@ -187,7 +186,7 @@ void AutoDetectProxy::Next() {
 bool AutoDetectProxy::DoConnect() {
   if (resolver_) {
     resolver_->Destroy(false);
-    resolver_ = NULL;
+    resolver_ = nullptr;
   }
   socket_ =
       Thread::Current()->socketserver()->CreateAsyncSocket(