Make PrivetTrafficDetector::CreateUDPSocketOnUIThread() standalone.

Split CreateUDPSocketOnUIThread() into a standalone function so less of
PrivetTrafficDetector lives on the UI thread.

Change-Id: Ide58478bb235d9c1da72fccd6b86da35cd3997af
Reviewed-on: https://chromium-review.googlesource.com/1177443
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583740}

chrome/browser/printing/cloud_print/privet_traffic_detector.cc

@@ -55,6 +55,17 @@ void GetNetworkListInBackground(
       base::BindOnce(std::move(callback), std::move(ip4_networks)));
 }
 
+void CreateUDPSocketOnUIThread(
+    content::BrowserContext* profile,
+    network::mojom::UDPSocketRequest request,
+    network::mojom::UDPSocketReceiverPtr receiver_ptr) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  network::mojom::NetworkContext* network_context =
+      content::BrowserContext::GetDefaultStoragePartition(profile)
+          ->GetNetworkContext();
+  network_context->CreateUDPSocket(std::move(request), std::move(receiver_ptr));
+}
+
 }  // namespace
 
 namespace cloud_print {
@@ -129,7 +140,7 @@ void PrivetTrafficDetector::Bind() {
   receiver_binding_.Bind(std::move(receiver_request));
   content::BrowserThread::PostTask(
       content::BrowserThread::UI, FROM_HERE,
-      base::BindOnce(&PrivetTrafficDetector::CreateUDPSocketOnUIThread, this,
+      base::BindOnce(&CreateUDPSocketOnUIThread, profile_,
                      mojo::MakeRequest(&socket_), std::move(receiver_ptr)));
 
   net::IPEndPoint multicast_addr =
@@ -148,16 +159,6 @@ void PrivetTrafficDetector::Bind() {
                                multicast_addr));
 }
 
-void PrivetTrafficDetector::CreateUDPSocketOnUIThread(
-    network::mojom::UDPSocketRequest request,
-    network::mojom::UDPSocketReceiverPtr receiver_ptr) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  network::mojom::NetworkContext* network_context =
-      content::BrowserContext::GetDefaultStoragePartition(profile_)
-          ->GetNetworkContext();
-  network_context->CreateUDPSocket(std::move(request), std::move(receiver_ptr));
-}
-
 void PrivetTrafficDetector::OnBindComplete(
     net::IPEndPoint multicast_addr,
     int rv,

chrome/browser/printing/cloud_print/privet_traffic_detector.h

@@ -55,12 +55,6 @@ class PrivetTrafficDetector
   void ScheduleRestart();
   void Restart(net::NetworkInterfaceList networks);
   void Bind();
-
-  // Called on the UI thread.
-  void CreateUDPSocketOnUIThread(
-      network::mojom::UDPSocketRequest request,
-      network::mojom::UDPSocketReceiverPtr receiver_ptr);
-
   void OnBindComplete(net::IPEndPoint multicast_addr,
                       int rv,
                       const base::Optional<net::IPEndPoint>& ip_address);
@@ -92,7 +86,8 @@ class PrivetTrafficDetector
   // Initialized on the UI thread, but only accessed on the IO thread.
   mojo::Binding<network::mojom::UDPSocketReceiver> receiver_binding_;
 
-  // Only accessed on the UI thread
+  // Initialized on the UI thread, but only accessed on the IO thread for the
+  // purpose of passing it back to the UI thread. Safe because it is const.
   content::BrowserContext* const profile_;
 
   base::WeakPtrFactory<PrivetTrafficDetector> weak_ptr_factory_;