Replace NULL with nullptr in all C++ files.

webrtc/p2p/base/transportdescriptionfactory.cc

Index: webrtc/p2p/base/transportdescriptionfactory.cc
diff --git a/webrtc/p2p/base/transportdescriptionfactory.cc b/webrtc/p2p/base/transportdescriptionfactory.cc
index 238e1b66a14b46d0be228c6f613237d4c3798d95..74ca81f69196de23c54b7f5a2e7b6ebfcd761138 100644
--- a/webrtc/p2p/base/transportdescriptionfactory.cc
+++ b/webrtc/p2p/base/transportdescriptionfactory.cc
@@ -46,7 +46,7 @@ TransportDescription* TransportDescriptionFactory::CreateOffer(
     // Fail if we can't create the fingerprint.
     // If we are the initiator set role to "actpass".
     if (!SetSecurityInfo(desc.get(), CONNECTIONROLE_ACTPASS)) {
-      return NULL;
+      return nullptr;
     }
   }
 
@@ -57,11 +57,11 @@ TransportDescription* TransportDescriptionFactory::CreateAnswer(
     const TransportDescription* offer,
     const TransportOptions& options,
     const TransportDescription* current_description) const {
-  // TODO(juberti): Figure out why we get NULL offers, and fix this upstream.
+  // TODO(juberti): Figure out why we get null offers, and fix this upstream.
   if (!offer) {
-    LOG(LS_WARNING) << "Failed to create TransportDescription answer " <<
-        "because offer is NULL";
-    return NULL;
+    LOG(LS_WARNING) << "Failed to create TransportDescription answer "
+                    << "because offer is null";
+    return nullptr;
   }
 
   std::unique_ptr<TransportDescription> desc(new TransportDescription());
@@ -88,14 +88,14 @@ TransportDescription* TransportDescriptionFactory::CreateAnswer(
           CONNECTIONROLE_PASSIVE : CONNECTIONROLE_ACTIVE;
 
       if (!SetSecurityInfo(desc.get(), role)) {
-        return NULL;
+        return nullptr;
       }
     }
   } else if (secure_ == SEC_REQUIRED) {
     // We require DTLS, but the other side didn't offer it. Fail.
     LOG(LS_WARNING) << "Failed to create TransportDescription answer "
                        "because of incompatible security settings";
-    return NULL;
+    return nullptr;
   }
 
   return desc.release();