BluetoothAdapterObserver::DeviceChanged is a catch-all event that gets called for all events that pertain to a device. This leads to clients having to keep the state of a device themselves to understand what changed when DeviceChanged is called. Some clients just assume that the DeviceChanged is called whenever an advertisement is received causing to incorrectly dispatch events.

// Called when the result of one of the following methods of the device
// |device| changes:
//  * GetAddress()               // We already have DeviceAddressChanged.
//  * GetAppearance()            // Should be part of "AdvertisementReceived"
//  * GetBluetoothClass()        // Should be part of "ClassicDeviceFound"
//  * GetInquiryRSSI()           // Should be part of "AdvertisementReceived"
//  * GetInquiryTxPower()        // Ditto.
//  * GetUUIDs()                 // Ditto.
//  * GetServiceData()           // Ditto.
//  * GetServiceDataUUIDs()      // Ditto.
//  * GetServiceDataForUUID()    // Ditto.
//  * GetManufacturerData()      // Ditto.
//  * GetManufacturerDataIDs()   // Ditto.
//  * GetManufacturerDataForID() // Ditto.
//  * GetAdvertisingDataFlags()  // Ditto.
//  * IsConnectable()            // Ditto.
//  * IsConnected()              // Should be part of DeviceConnectionStateChanged
//  * IsConnecting()             // Ditto.
//  * IsGattConnected()          // Ditto.
//  * IsPaired()                 // We already have DevicePairedChanged