Tag sockets in FlipperSocketImpl (#3928)

Summary:
Resolves https://github.com/facebook/flipper/issues/3926. Open to suggestions on the tag value, just sort of picked one that could be pointed to for anyone that wants to track these in their apps.

## Changelog

Tag sockets used by Flipper to fix strict mode warnings about untagged sockets.

Pull Request resolved: https://github.com/facebook/flipper/pull/3928

Test Plan:
Edit FlipperSampleApplication.java with the following:

```
public class FlipperSampleApplication extends Application {
  Override
  public void onCreate() {

    StrictMode.setThreadPolicy(
            new StrictMode.ThreadPolicy.Builder()
                    .detectAll()
                    .penaltyLog()
                    .build()
    );
    StrictMode.setVmPolicy(
            new StrictMode.VmPolicy.Builder()
                    .detectAll()
                    .penaltyLog()
                    .build()
    );
...
```

That will enable strict mode. Now build/launch the sample application.

Use adb logcat to inspect warnings:

```
 adb logcat -s StrictMode
```

Without tagging the socket, the following warning should be observed:

```
D/StrictMode: StrictMode policy violation: android.os.strictmode.UntaggedSocketViolation: Untagged socket detected; use TrafficStats.setTrafficStatsTag() to track all network usage
```

After applying the fix, that warning should go away.

Reviewed By: lblasa

Differential Revision: D38280819

Pulled By: passy

fbshipit-source-id: 0c841b13237cbcb0ff8b8226fb44655a74b775c6

android/src/main/java/com/facebook/flipper/android/DelegatingSocketFactory.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2014 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.facebook.flipper.android;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.Socket;
+import javax.net.SocketFactory;
+
+/**
+ * A {@link SocketFactory} that delegates calls. Sockets can be configured after creation by
+ * overriding {@link #configureSocket}.
+ */
+class DelegatingSocketFactory extends SocketFactory {
+  private final SocketFactory delegate;
+
+  DelegatingSocketFactory(SocketFactory delegate) {
+    this.delegate = delegate;
+  }
+
+  @Override
+  public Socket createSocket() throws IOException {
+    Socket socket = delegate.createSocket();
+    return configureSocket(socket);
+  }
+
+  @Override
+  public Socket createSocket(String host, int port) throws IOException {
+    Socket socket = delegate.createSocket(host, port);
+    return configureSocket(socket);
+  }
+
+  @Override
+  public Socket createSocket(String host, int port, InetAddress localAddress, int localPort)
+      throws IOException {
+    Socket socket = delegate.createSocket(host, port, localAddress, localPort);
+    return configureSocket(socket);
+  }
+
+  @Override
+  public Socket createSocket(InetAddress host, int port) throws IOException {
+    Socket socket = delegate.createSocket(host, port);
+    return configureSocket(socket);
+  }
+
+  @Override
+  public Socket createSocket(InetAddress host, int port, InetAddress localAddress, int localPort)
+      throws IOException {
+    Socket socket = delegate.createSocket(host, port, localAddress, localPort);
+    return configureSocket(socket);
+  }
+
+  protected Socket configureSocket(Socket socket) {
+    // No-op by default.
+    return socket;
+  }
+}

android/src/main/java/com/facebook/flipper/android/FlipperSocketImpl.java

@@ -7,6 +7,7 @@
 
 package com.facebook.flipper.android;
 
+import android.net.TrafficStats;
 import android.util.Log;
 import com.facebook.flipper.BuildConfig;
 import com.facebook.flipper.core.FlipperObject;
@@ -17,6 +18,7 @@ import com.facebook.soloader.SoLoader;
 import java.io.BufferedInputStream;
 import java.io.FileInputStream;
 import java.io.InputStream;
+import java.net.Socket;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.security.InvalidAlgorithmParameterException;
@@ -100,7 +102,14 @@ class FlipperSocketImpl extends WebSocketClient implements FlipperSocket {
 
         SSLSocketFactory factory = sslContext.getSocketFactory();
 
-        this.setSocketFactory(factory);
+        this.setSocketFactory(
+            new DelegatingSocketFactory(factory) {
+              @Override
+              protected Socket configureSocket(Socket socket) {
+                TrafficStats.setThreadStatsTag(SOCKET_TAG);
+                return socket;
+              }
+            });
       }
 
       this.connect();

android/src/main/java/com/facebook/flipper/core/FlipperSocket.java

@@ -9,6 +9,9 @@ package com.facebook.flipper.core;
 
 public interface FlipperSocket {
 
+  /** The value used by Flipper to tag sockets, visible to {@link android.net.TrafficStats}. */
+  int SOCKET_TAG = 0x000090000;
+
   /** Connect to the endpoint. */
   void flipperConnect();