webauthn: allow USB or QR caBLE transactions to preempt FCM.

If an FCM transactions triggers but then one happens to plug in a USB
cable, the mobile side hits this DCHECK. But it's fine to cancel the FCM
transaction if the user has taken action to try another channel.

Also, drop the notification if the FCM transaction is deleted.

BUG=1002262

Change-Id: I857016e31a0a3d56ee17f54ca4eecb4e6b3f9fdf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2511974Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823842}

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

@@ -526,6 +526,13 @@ class CableAuthenticator {
         notificationManager.notify(NOTIFICATION_CHANNEL_ID, ID, builder.build());
     }
 
+    @CalledByNative
+    public static void dropNotification() {
+        Context context = ContextUtils.getApplicationContext();
+        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(context);
+        notificationManager.cancel(NOTIFICATION_CHANNEL_ID, ID);
+    }
+
     @NativeMethods
     interface Natives {
         /**

chrome/android/features/cablev2_authenticator/native/cablev2_authenticator_android.cc

@@ -202,6 +202,12 @@ class AndroidPlatform : public device::cablev2::authenticator::Platform {
       : env_(env),
         interaction_needed_callback_(std::move(interaction_needed_callback)) {}
 
+  ~AndroidPlatform() override {
+    if (notification_showing_) {
+      Java_CableAuthenticator_dropNotification(env_);
+    }
+  }
+
   // Platform:
   void MakeCredential(std::unique_ptr<MakeCredentialParams> params) override {
     DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
@@ -289,6 +295,7 @@ class AndroidPlatform : public device::cablev2::authenticator::Platform {
   void NeedInteractive() {
     DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
+    notification_showing_ = true;
     std::move(interaction_needed_callback_)
         .Run(base::BindOnce(&AndroidPlatform::OnInteractionReady,
                             weak_factory_.GetWeakPtr()));
@@ -299,11 +306,13 @@ class AndroidPlatform : public device::cablev2::authenticator::Platform {
   void OnInteractionReady(ScopedJavaGlobalRef<jobject> cable_authenticator) {
     DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
     DCHECK(!cable_authenticator_);
+    DCHECK(notification_showing_);
     DCHECK(env_->IsInstanceOf(
         cable_authenticator.obj(),
         org_chromium_chrome_browser_webauth_authenticator_CableAuthenticator_clazz(
             env_)));
     cable_authenticator_ = std::move(cable_authenticator);
+    notification_showing_ = false;
 
     DCHECK(static_cast<bool>(pending_make_credential_) ^
            static_cast<bool>(pending_get_assertion_));
@@ -315,6 +324,7 @@ class AndroidPlatform : public device::cablev2::authenticator::Platform {
   }
 
   JNIEnv* const env_;
+  bool notification_showing_ = false;
   ScopedJavaGlobalRef<jobject> cable_authenticator_;
   std::unique_ptr<MakeCredentialParams> pending_make_credential_;
   std::unique_ptr<GetAssertionParams> pending_get_assertion_;
@@ -442,7 +452,6 @@ static void JNI_CableAuthenticator_StartUSB(
   DCHECK(!global_data.usb_callback);
   global_data.usb_callback = transport->GetCallback();
 
-  DCHECK(!global_data.current_transaction);
   global_data.current_transaction =
       device::cablev2::authenticator::TransactWithPlaintextTransport(
           std::make_unique<AndroidPlatform>(env, cable_authenticator),
@@ -464,7 +473,6 @@ static jboolean JNI_CableAuthenticator_StartQR(
     return false;
   }
 
-  DCHECK(!global_data.current_transaction);
   global_data.current_transaction =
       device::cablev2::authenticator::TransactFromQRCode(
           std::make_unique<AndroidPlatform>(env, cable_authenticator),