bluetooth: Implement hardware filtering on macOS

device/bluetooth/bluetooth_low_energy_discovery_manager_mac.h

Index: device/bluetooth/bluetooth_low_energy_discovery_manager_mac.h
diff --git a/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.h b/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.h
index 20d63a123f92515ebb4a622f85e3e762ba81cf44..7c12cd2e4e4b698b9bd72216b01e10b12e81d3ad 100644
--- a/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.h
+++ b/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.h
@@ -42,7 +42,11 @@ class BluetoothLowEnergyDiscoveryManagerMac {
   // Initiates a discovery session.
   // BluetoothLowEnergyDeviceMac objects discovered within a previous
   // discovery session will be invalid.
-  virtual void StartDiscovery(BluetoothDevice::UUIDList services_uuids);
+  virtual void StartDiscovery(std::set<BluetoothUUID> services_uuids);
+
+  // Updates the scan request to stop scanning for |uuids_to_remove| if
+  // no other filter is scanning for those uuids.

[Jeffrey Yasskin, 2016/08/23 21:37:04]

We don't have the concept of a filter in this class's interface, so you should
describe the condition some other way. Maybe say that StartDiscovery() adds the
UUIDs to a multiset of active UUIDs,and RemoveDiscoveryUUIDs() removes them, and
discovery will be active for any UUID in that multiset?

+  virtual void RemoveDiscoveryUUIDs(std::set<BluetoothUUID> uuids_to_remove);
 
   // Stops a discovery session.
   virtual void StopDiscovery();
@@ -84,8 +88,10 @@ class BluetoothLowEnergyDiscoveryManagerMac {
   // waiting for Bluetooth to turn on.
   bool pending_;
 
-  // List of service UUIDs to scan.
-  BluetoothDevice::UUIDList services_uuids_;
+  // List of service UUIDs to scan for to the number of filters that have that

[Jeffrey Yasskin, 2016/08/23 21:37:04]

s/list/map/?

+  // UUID.
+  std::unordered_map<device::BluetoothUUID, size_t, device::BluetoothUUIDHash>
+      scan_uuids_to_filter_count_;
 
   DISALLOW_COPY_AND_ASSIGN(BluetoothLowEnergyDiscoveryManagerMac);
 };