[Fast Pair] Write account key after pairing change

Currently Fast Pair attempts to write the account key before
DevicePairedChanged() is called. This flow can cause GATT failures for
some devices (Pixel Buds Pros). This change moves the writing of the
account key into DevicePairedChanged(). DevicePairedChanged() uses the additional data in the Fast Pair Device object to differentiate between V1 and V2 fast pair devices.

unit tests

Tested: Tested manually DUT with allegro and other devices. Updated
Change-Id: I04024f2c5be4b37e221984de215983ccb16e1714
Fixed: b/244337054 b/234166201
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3961635
Reviewed-by: Juliet Lévesque <julietlevesque@google.com>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Alex Kingsborough <akingsb@google.com>
Cr-Commit-Position: refs/heads/main@{#1069037}

ash/quick_pair/pairing/fast_pair/fast_pair_pairer_impl.cc

@@ -419,9 +419,8 @@ void FastPairPairerImpl::OnParseDecryptedPasskey(
 
   QP_LOG(INFO) << __func__ << ": Passkeys match, confirming pairing";
   pairing_device->ConfirmPairing();
-  std::move(paired_callback_).Run(device_);
-  adapter_->RemovePairingDelegate(this);
-  AttemptSendAccountKey();
+  // DevicePairedChanged() is expected to be called following pairing
+  // confirmation.
 }
 
 void FastPairPairerImpl::AttemptSendAccountKey() {
@@ -628,14 +627,23 @@ void FastPairPairerImpl::DevicePairedChanged(device::BluetoothAdapter* adapter,
   if (!new_paired_status || !paired_callback_)
     return;
 
-  // This covers the case where we are pairing a v1 device and are using the
-  // Bluetooth pairing dialog to do it.
   if (device->GetAddress() == device_->ble_address ||
       device->GetAddress() == device_->classic_address()) {
-    QP_LOG(INFO) << __func__ << ": Completing pairing procedure";
+    QP_LOG(INFO) << __func__ << ": Completing pairing procedure " << device_;
     std::move(paired_callback_).Run(device_);
 
-    if (pairing_procedure_complete_) {
+    // For V2 devices we still need to remove the Pairing Delegate and write the
+    // account key. `AttemptSendAccountKey()` will call
+    // |pairing_procedure_complete_| whereas V1 devices need to run the callback
+    // in this function since they don't write account keys, and their pairing
+    // procedure is not complete at this point.
+    if (device_->version().has_value() &&
+        device_->version().value() == DeviceFastPairVersion::kHigherThanV1) {
+      adapter_->RemovePairingDelegate(this);
+      AttemptSendAccountKey();
+    } else if (pairing_procedure_complete_) {
+      // This covers the case where we are pairing a v1 device and are using the
+      // Bluetooth pairing dialog to do it.
       std::move(pairing_procedure_complete_).Run(device_);
     }
   }