webauthn: only record caBLE v1 event if v1 data present.

r745162 adds a v1 event in FidoCableDiscovery::OnStartDiscoverySession,
but it's recorded unconditionally. With caBLE v2, there might not be v1
data in play.

Change-Id: Ie0aa18f10137f028c4ef06f2ee8d00fc5a19490b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2107424
Commit-Queue: Adam Langley <agl@chromium.org>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Auto-Submit: Adam Langley <agl@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#751063}

device/fido/cable/fido_cable_discovery.cc

@@ -499,7 +499,9 @@ void FidoCableDiscovery::StartCableDiscovery() {
 void FidoCableDiscovery::OnStartDiscoverySession(
     std::unique_ptr<BluetoothDiscoverySession> session) {
   FIDO_LOG(DEBUG) << "Discovery session started.";
-  RecordCableV1DiscoveryEventOnce(CableV1DiscoveryEvent::kScanningStarted);
+  if (has_v1_discovery_data_) {
+    RecordCableV1DiscoveryEventOnce(CableV1DiscoveryEvent::kScanningStarted);
+  }
   SetDiscoverySession(std::move(session));
   // Advertising is delayed by 500ms to ensure that any UI has a chance to
   // appear as we don't want to start broadcasting without the user being