webauthn: a batch of caBLE Java cleanups.

I'm flushing my queue of niggles that I've noticed over time:

1. The |Callback| interface in |CableAuthenticator| is moot. It always
   calls |CableAuthenticatorUI|, which is in the same package. There's
   even an |mUi| member already.
2. In a couple of cases calls were moved to the |mTaskRunner| thread,
   but since the Mojo network interface only works on the UI thread, we
   know that's the UI thread now and thus the transition is moot.
   Replace them with asserts.
3. A number of methods were more public than needed. If not specified,
   Java defaults to package-private, which works for a lot of cases
   here.

BUG=1002262

Change-Id: Ieee4ab7fc9c1f3ae339d661b2ed5ce6e1adb28ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2531178
Commit-Queue: Adam Langley <agl@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#826980}

chrome/android/features/cablev2_authenticator/java/src/org/chromium/chrome/browser/webauth/authenticator/CableAuthenticator.java

@@ -83,7 +83,6 @@ class CableAuthenticator {
 
     private final Context mContext;
     private final CableAuthenticatorUI mUi;
-    private final Callback mCallback;
     private final SingleThreadTaskRunner mTaskRunner;
 
     public enum Result {
@@ -94,27 +93,11 @@ class CableAuthenticator {
         OTHER,
     }
 
-    // Callbacks notifying the UI of certain CableAuthenticator state changes. These may run on any
-    // thread.
-    public interface Callback {
-        // Invoked when the authenticator has completed a handshake with a client device.
-        void onAuthenticatorConnected();
-        // Invoked when a transaction has completed. The response may still be transmitting and
-        // onComplete will follow.
-        void onAuthenticatorResult(Result result);
-        // Invoked when the authenticator has finished. The UI should be dismissed at this point.
-        void onComplete();
-        // Called when an informative status update is available. The argument has the same values
-        // as the Status enum from v2_authenticator.h.
-        void onStatus(int code);
-    }
-
     public CableAuthenticator(Context context, CableAuthenticatorUI ui, long networkContext,
             long registration, String activityClassName, boolean isFcmNotification,
             UsbAccessory accessory) {
         mContext = context;
         mUi = ui;
-        mCallback = ui;
 
         // networkContext can only be used from the UI thread, therefore all
         // short-lived work is done on that thread.
@@ -169,7 +152,7 @@ class CableAuthenticator {
     // as the Status enum from v2_authenticator.h.
     @CalledByNative
     public void onStatus(int code) {
-        mCallback.onStatus(code);
+        mUi.onStatus(code);
     }
 
     @CalledByNative
@@ -306,10 +289,10 @@ class CableAuthenticator {
     @CalledByNative
     public void onComplete() {
         assert mTaskRunner.belongsToCurrentThread();
-        mCallback.onComplete();
+        mUi.onComplete();
     }
 
-    public void onActivityResult(int requestCode, int resultCode, Intent data) {
+    void onActivityResult(int requestCode, int resultCode, Intent data) {
         Log.i(TAG, "onActivityResult " + requestCode + " " + resultCode);
 
         Result result = Result.OTHER;
@@ -332,10 +315,10 @@ class CableAuthenticator {
                 Log.i(TAG, "invalid requestCode: " + requestCode);
                 assert (false);
         }
-        mCallback.onAuthenticatorResult(result);
+        mUi.onAuthenticatorResult(result);
     }
 
-    public boolean onRegisterResponse(int resultCode, Intent data) {
+    private boolean onRegisterResponse(int resultCode, Intent data) {
         if (resultCode != Activity.RESULT_OK || data == null) {
             Log.e(TAG, "Failed with result code" + resultCode);
             onAuthenticatorAssertionResponse(CTAP2_ERR_OPERATION_DENIED, null, null, null, null);
@@ -384,7 +367,7 @@ class CableAuthenticator {
         return true;
     }
 
-    public boolean onSignResponse(int resultCode, Intent data) {
+    private boolean onSignResponse(int resultCode, Intent data) {
         if (resultCode != Activity.RESULT_OK || data == null) {
             Log.e(TAG, "Failed with result code" + resultCode);
             onAuthenticatorAssertionResponse(CTAP2_ERR_OPERATION_DENIED, null, null, null, null);
@@ -457,15 +440,14 @@ class CableAuthenticator {
      * @param value contents of the QR code, which will be a valid caBLE
      *              URL, i.e. "fido://"...
      */
-    public void onQRCode(String value) {
-        mTaskRunner.postTask(() -> {
-            CableAuthenticatorJni.get().startQR(this, getName(), value);
-            // TODO: show the user an error if that returned false.
-            // that indicates that the QR code was invalid.
-        });
+    void onQRCode(String value) {
+        assert mTaskRunner.belongsToCurrentThread();
+        CableAuthenticatorJni.get().startQR(this, getName(), value);
+        // TODO: show the user an error if that returned false.
+        // that indicates that the QR code was invalid.
     }
 
-    public void unlinkAllDevices() {
+    void unlinkAllDevices() {
         Log.i(TAG, "Unlinking devices");
         byte[] newStateBytes = CableAuthenticatorJni.get().unlink();
         SharedPreferences prefs = ContextUtils.getAppSharedPreferences();
@@ -475,8 +457,9 @@ class CableAuthenticator {
                 .apply();
     }
 
-    public void close() {
-        mTaskRunner.postTask(() -> { CableAuthenticatorJni.get().stop(); });
+    void close() {
+        assert mTaskRunner.belongsToCurrentThread();
+        CableAuthenticatorJni.get().stop();
     }
 
     static String getName() {
@@ -486,7 +469,7 @@ class CableAuthenticator {
     /**
      * onCloudMessage is called by {@link CableAuthenticatorUI} when a GCM message is received.
      */
-    public static void onCloudMessage(
+    static void onCloudMessage(
             long event, long systemNetworkContext, long registration, String activityClassName) {
         setup(registration, activityClassName, systemNetworkContext);
         CableAuthenticatorJni.get().onCloudMessage(event);

chrome/android/features/cablev2_authenticator/java/src/org/chromium/chrome/browser/webauth/authenticator/CableAuthenticatorUI.java

@@ -36,8 +36,8 @@ import java.lang.ref.WeakReference;
 /**
  * A fragment that provides a UI for scanning caBLE v2 QR codes.
  */
-public class CableAuthenticatorUI extends Fragment
-        implements OnClickListener, QRScanDialog.Callback, CableAuthenticator.Callback {
+public class CableAuthenticatorUI
+        extends Fragment implements OnClickListener, QRScanDialog.Callback {
     private enum Mode {
         QR, // Triggered from Settings; can scan QR code to start handshake.
         FCM, // Triggered by user selecting notification; handshake already running.
@@ -188,8 +188,7 @@ public class CableAuthenticatorUI extends Fragment
         mAuthenticator.onQRCode(value);
     }
 
-    @Override
-    public void onStatus(int code) {
+    void onStatus(int code) {
         if (mMode != Mode.QR) {
             // In FCM mode, the handshake is done before the UI appears. For
             // USB everything should happen immediately.
@@ -230,12 +229,10 @@ public class CableAuthenticatorUI extends Fragment
         mAuthenticator.onActivityResult(requestCode, resultCode, data);
     }
 
-    @Override
     @SuppressLint("SetTextI18n")
-    public void onAuthenticatorConnected() {}
+    void onAuthenticatorConnected() {}
 
-    @Override
-    public void onAuthenticatorResult(CableAuthenticator.Result result) {
+    void onAuthenticatorResult(CableAuthenticator.Result result) {
         getActivity().runOnUiThread(() -> {
             // TODO: Temporary UI, needs i18n.
             String toast = "An error occured. Please try again.";
@@ -259,8 +256,7 @@ public class CableAuthenticatorUI extends Fragment
         });
     }
 
-    @Override
-    public void onComplete() {
+    void onComplete() {
         getActivity().runOnUiThread(() -> { getActivity().finish(); });
     }
 

chrome/android/features/cablev2_authenticator/java/src/org/chromium/chrome/browser/webauth/authenticator/CameraView.java

@@ -68,7 +68,7 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback {
      * Called to indicate that the callback that was passed to the constructor has finished
      * processing and thus is free to receive another camera frame.
      */
-    public void rearmCallback() {
+    void rearmCallback() {
         ThreadUtils.assertOnUiThread();
 
         if (mCamera != null) {

chrome/android/features/cablev2_authenticator/java/src/org/chromium/chrome/browser/webauth/authenticator/QRScanDialog.java

@@ -31,7 +31,7 @@ import java.nio.ByteBuffer;
  * Displays a preview of what the default (rear) camera can see and processes images for QR
  * codes. Closes once an applicable QR code has been found.
  */
-public class QRScanDialog extends DialogFragment implements Camera.PreviewCallback {
+class QRScanDialog extends DialogFragment implements Camera.PreviewCallback {
     /**
      * FIDO QR codes begin with this prefix. This class will ignore QR codes that don't match
      * this.