Repository: flutter
Issue: PluginRegistry.ActivityResultListener: not triggered
Labels: engine,P2,a: plugins,team-engine,triaged-engine

## Steps to Reproduce


1. Create a Flutter package in java
2. In plugin class add a Activity result listener
3. In onMethodCall call startActivityForResult
4. In Activity called, at a certain point, call setResult and finish

Issue is the `onActivityResult' plugin is not triggered when Activity child call finish.


here's the code of parent `MyBarcodeScannerPlugin` ...
```java
    public class MyBarcodeScannerPlugin implements MethodCallHandler, PluginRegistry.ActivityResultListener {
      private final Activity activity;
      private Result result;

      public static void registerWith(Registrar registrar) {
        final MethodChannel channel = new MethodChannel(registrar.messenger(),    "my_barcode_scanner");

        final MyBarcodeScannerPlugin plugin = new MyBarcodeScannerPlugin(registrar.activity());

        channel.setMethodCallHandler(plugin);
        registrar.addActivityResultListener(plugin);
      }

      private MyBarcodeScannerPlugin(Activity activity) {
        this.activity = activity;
      }


      @Override
      public void onMethodCall(MethodCall call, Result result) {
        if (call.method.equals("scan")) {
          this.result = result;
          showBarcodeView(activity);
        } else {
          result.notImplemented();
        }
      }

      private void showBarcodeView(Activity activity) {
        Intent intent = new Intent(activity, MyBarcodeScannerActivity.class);
        activity.startActivityForResult(intent, 100);
      }

      @Override
      public boolean onActivityResult(int requestCode, int resultCode, Intent data) {
        // IT DOES NOT FIRE !
        if (requestCode == 100) {
          if (resultCode == Activity.RESULT_OK) {
            this.result.success("");
          } else {
            String errorCode = data.getStringExtra("ERROR_CODE");
            this.result.error(errorCode, null, null);
          }
          return true;
        }
        return false;
      }
    }
```

And here's the child activity that finish when user deny permission...
```java
    public class MyBarcodeScannerActivity extends AppCompatActivity {
        ...
        ...
        private void finishWithError(String errorCode) {
            Intent intent = new Intent();
            intent.putExtra("ERROR_CODE", errorCode);
            setResult(Activity.RESULT_CANCELED, intent);
            finish();
        }
        ...
        public void onRequestPermissionsResult(int requestCode, String  permissions[], int[] grantResults) {
            switch (requestCode) {
                case REQUEST_CAMERA:
                    if (grantResults.length > 0) {
                        boolean cameraAccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                        if (cameraAccepted){
                        }else {
                            finishWithError("PERMISSION_NOT_GRANTED");
                        }
                    }
                    break;
            }
        }
    }
```


<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
flutter doctor -v
[√] Flutter (Channel stable, v1.0.0, on Microsoft Windows [Versione 10.0.16299.904], locale it-IT)
    • Flutter version 1.0.0 at C:\dati\Flutter\flutter
    • Framework revision 5391447fae (8 weeks ago), 2018-11-29 19:41:26 -0800
    • Engine revision 7375a0f414
    • Dart version 2.1.0 (build 2.1.0-dev.9.4 f9ebf21297)

[√] Android toolchain - develop for Android devices (Android SDK 28.0.3)
    • Android SDK at C:/Users/...
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-28, build-tools 28.0.3
    • ANDROID_HOME = C:/Users/...
    • Java binary at: C:\dati\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b02)

[√] Android Studio (version 3.1)
    • Android Studio at C:\dati\Android\Android Studio
    • Flutter plugin version 29.0.1
    • Dart plugin version 173.4700
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b02)

[√] IntelliJ IDEA Community Edition (version 2018.1)
    • IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2018.1.4
    • Flutter plugin version 25.0.2
    • Dart plugin version 181.4892.1

[√] VS Code, 64-bit edition (version 1.23.1)
    • VS Code at C:\Program Files\Microsoft VS Code
    • Flutter extension version 2.13.2

[√] Connected device (1 available)
    • Redmi Note 5 • 8614d893 • android-arm64 • Android 8.1.0 (API 27)

```