Add UMA for the number of devices in the chooser when a device is paired

content/browser/bluetooth/bluetooth_device_chooser_controller.cc

Index: content/browser/bluetooth/bluetooth_device_chooser_controller.cc
diff --git a/content/browser/bluetooth/bluetooth_device_chooser_controller.cc b/content/browser/bluetooth/bluetooth_device_chooser_controller.cc
index 6a0e22a8eb8277c5a6bad3e9f4ddd816aae8fc9b..65c13c29b780001a0f538ca7e43567b314c3f0da 100644
--- a/content/browser/bluetooth/bluetooth_device_chooser_controller.cc
+++ b/content/browser/bluetooth/bluetooth_device_chooser_controller.cc
@@ -429,8 +429,10 @@ void BluetoothDeviceChooserController::AddFilteredDevice(
         MatchesFilters(device_name ? &device_name.value() : nullptr,
                        device.GetUUIDs(), options_->filters)) {
       base::Optional<int8_t> rssi = device.GetInquiryRSSI();
+      std::string device_id = device.GetAddress();
+      device_ids_.insert(device_id);

[Reilly Grant (use Gerrit), 2016/12/19 20:52:17]

I was going to note that you should call device_ids_.erase() whenever you call
BluetoothChooser::RemoveDevice() but then noticed that there is no code that
calls that function, so I suggest removing it in a follow-up patch.

[juncai, 2016/12/19 22:16:13]

Thanks! I filed a bug for it:
https://bugs.chromium.org/p/chromium/issues/detail?id=675720

       chooser_->AddOrUpdateDevice(
-          device.GetAddress(), !!device.GetName() /* should_update_name */,
+          device_id, !!device.GetName() /* should_update_name */,
           device.GetNameForDisplay(), device.IsGattConnected(),
           web_bluetooth_service_->IsDevicePaired(device.GetAddress()),
           rssi ? CalculateSignalStrengthLevel(rssi.value()) : -1);
@@ -501,6 +503,8 @@ void BluetoothDeviceChooserController::StartDeviceDiscovery() {
     return;
   }
 
+  device_ids_.clear();
+
   scanning_start_time_ = base::TimeTicks::Now();
 
   chooser_->ShowDiscoveryState(BluetoothChooser::DiscoveryState::DISCOVERING);
@@ -588,6 +592,7 @@ void BluetoothDeviceChooserController::OnBluetoothChooserEvent(
       PostErrorCallback(blink::mojom::WebBluetoothResult::CHOOSER_CANCELLED);
       break;
     case BluetoothChooser::Event::SELECTED:
+      RecordNumOfDevices(options_->accept_all_devices, device_ids_.size());
       // RecordRequestDeviceOutcome is called in the callback, because the
       // device may have vanished.
       PostSuccessCallback(device_address);