Implement Wi-Fi QR code scanner flow.

1. Implements WifiNetworkConfig Wi-Fi connection method
2. Shows error message when the QR code is not valid and hides it after 2s
3. In configurator mode, launchs AddDeviceFragment for a valid QR code
4. In enrollee mode, connects Wi-Fi for a valid QR code

Bug: 118794978
Test: manual test
      atest WifiQrCodetest
      atest WifiDppConfiguratorActivityTest
      atest WifiDppEnrolleeActivityTest
      atest WifiDppQrCodeScannerFragmentTest

Change-Id: Ie4731b22df295c60906156d33ea28dad9c084ce4

src/com/android/settings/wifi/qrcode/QrCamera.java

@@ -152,6 +152,15 @@ public class QrCamera extends Handler {
          * @param transform The transform to apply to the content of preview
          */
         void setTransform(Matrix transform);
+
+        /**
+         * Verify QR code is valid or not. The camera will stop scanning if this callback returns
+         * true.
+         *
+         * @param qrCode The result QR code after decoding.
+         * @return Returns true if qrCode hold valid information.
+         */
+        boolean isValid(String qrCode);
     }
 
     private void setCameraParameter() {
@@ -245,7 +254,9 @@ public class QrCamera extends Handler {
                         mReader.reset();
                     }
                     if (qrCode != null) {
-                        return qrCode.getText();
+                        if (mScannerCallback.isValid(qrCode.getText())) {
+                            return qrCode.getText();
+                        }
                     }
                 } catch (InterruptedException e) {
                     Thread.currentThread().interrupt();