Bug 1622816 - Ensure network is always available in TestRunnerActivity r=geckoview-reviewers,agi

When running mochitests on real hardware, we sometimes lose the network,
causing strange timeouts. It's better if we crash immediately in those
situations to avoid confusion.

Differential Revision: https://phabricator.services.mozilla.com/D67383

--HG--
extra : moz-landing-system : lando

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/TestRunnerActivity.java

@@ -19,8 +19,12 @@ import org.mozilla.geckoview.WebExtensionController;
 import org.mozilla.geckoview.WebRequestError;
 
 import android.app.Activity;
+import android.content.Context;
 import android.content.Intent;
 import android.graphics.SurfaceTexture;
+import android.net.ConnectivityManager;
+import android.net.Network;
+import android.net.NetworkInfo;
 import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.NonNull;
@@ -257,12 +261,29 @@ public class TestRunnerActivity extends Activity {
         }
     }
 
+    private void ensureNetworkAvailable() {
+        ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
+        cm.registerDefaultNetworkCallback(new ConnectivityManager.NetworkCallback() {
+            @Override
+            public void onLost(Network network) {
+                throw new RuntimeException("Network has been lost");
+            }
+        });
+
+        NetworkInfo network = cm.getActiveNetworkInfo();
+        if (network == null || !network.isConnected()) {
+            throw new RuntimeException("No network available");
+        }
+    }
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
         final Intent intent = getIntent();
 
+        ensureNetworkAvailable();
+
         if (sRuntime == null) {
             final GeckoRuntimeSettings.Builder runtimeSettingsBuilder =
                 new GeckoRuntimeSettings.Builder();