Add callback for Connection/Disconnection to Metro

Reviewed By: bnham

Differential Revision: D6447126

fbshipit-source-id: d4c8a4dfb65c2a378f7fe696c8617ff5f3c6cb68

ReactAndroid/src/main/java/com/facebook/react/devsupport/DevServerHelper.java

@@ -25,6 +25,7 @@ import com.facebook.react.modules.systeminfo.AndroidInfoHelpers;
 import com.facebook.react.packagerconnection.FileIoHandler;
 import com.facebook.react.packagerconnection.JSPackagerClient;
 import com.facebook.react.packagerconnection.NotificationOnlyHandler;
+import com.facebook.react.packagerconnection.ReconnectingWebSocket.ConnectionCallback;
 import com.facebook.react.packagerconnection.RequestHandler;
 import com.facebook.react.packagerconnection.RequestOnlyHandler;
 import com.facebook.react.packagerconnection.Responder;
@@ -92,6 +93,8 @@ public class DevServerHelper {
   }
 
   public interface PackagerCommandListener {
+    void onPackagerConnected();
+    void onPackagerDisconnected();
     void onPackagerReloadCommand();
     void onPackagerDevMenuCommand();
     void onCaptureHeapCommand(final Responder responder);
@@ -163,10 +166,24 @@ public class DevServerHelper {
         });
         handlers.putAll(new FileIoHandler().handlers());
 
+        ConnectionCallback onPackagerConnectedCallback =
+          new ConnectionCallback() {
+              @Override
+              public void onConnected() {
+                commandListener.onPackagerConnected();
+              }
+
+              @Override
+              public void onDisconnected() {
+                commandListener.onPackagerDisconnected();
+              }
+            };
+
         mPackagerClient = new JSPackagerClient(
             clientId,
             mSettings.getPackagerConnectionSettings(),
-            handlers);
+            handlers,
+            onPackagerConnectedCallback);
         mPackagerClient.init();
 
         return null;

ReactAndroid/src/main/java/com/facebook/react/devsupport/DevSupportManagerImpl.java

@@ -723,6 +723,16 @@ public class DevSupportManagerImpl implements
     return mLastErrorStack;
   }
 
+  @Override
+  public void onPackagerConnected() {
+    // No-op
+  }
+
+  @Override
+  public void onPackagerDisconnected() {
+    // No-op
+  }
+
   @Override
   public void onPackagerReloadCommand() {
     // Disable debugger to resume the JsVM & avoid thread locks while reloading