arc: bluetooth: Add/Remove BT observer only when ARC is ready

The current implementation make arc_bluetooth_bridge to be
a bluetooth observer all the time. This lead to unnessary
work when ARC is not ready.

This patch changes that by register arc_bluetooth_bridge
to be a bluetooth observer when arc is ready and unregister
when arc is gone

BUG=635578
TEST=No log spam when there is no arc support

Review-Url: https://codereview.chromium.org/2223203002
Cr-Commit-Position: refs/heads/master@{#410828}

components/arc/bluetooth/arc_bluetooth_bridge.cc

@@ -180,13 +180,12 @@ namespace arc {
 ArcBluetoothBridge::ArcBluetoothBridge(ArcBridgeService* bridge_service)
     : ArcService(bridge_service), binding_(this), weak_factory_(this) {
   if (BluetoothAdapterFactory::IsBluetoothAdapterAvailable()) {
-    VLOG(1) << "registering bluetooth adapter";
+    VLOG(1) << "Registering bluetooth adapter.";
     BluetoothAdapterFactory::GetAdapter(base::Bind(
         &ArcBluetoothBridge::OnAdapterInitialized, weak_factory_.GetWeakPtr()));
   } else {
-    VLOG(1) << "no bluetooth adapter available";
+    VLOG(1) << "No bluetooth adapter available.";
   }
-
   arc_bridge_service()->bluetooth()->AddObserver(this);
 }
 
@@ -207,7 +206,14 @@ void ArcBluetoothBridge::OnAdapterInitialized(
   // so our adapter uses BlueZ.
   bluetooth_adapter_ =
       static_cast<bluez::BluetoothAdapterBlueZ*>(adapter.get());
-  bluetooth_adapter_->AddObserver(this);
+
+  // The ARC instance was ready before the Bluetooth adapter, hence we didn't
+  // register ourselves as an observer with it then. Since our adapter is
+  // ready, we should register it now.
+  if (!bluetooth_adapter_->HasObserver(this) &&
+      arc_bridge_service()->bluetooth()->instance()) {
+    bluetooth_adapter_->AddObserver(this);
+  }
 }
 
 void ArcBluetoothBridge::OnInstanceReady() {
@@ -218,7 +224,19 @@ void ArcBluetoothBridge::OnInstanceReady() {
                << "but no bluetooth instance found";
     return;
   }
+
   bluetooth_instance->Init(binding_.CreateInterfacePtrAndBind());
+
+  // The Bluetooth adapter was ready before the ARC instance, hence we didn't
+  // register ourselves as an observer with it then. Since our instance is
+  // ready, we should register it now.
+  if (bluetooth_adapter_ && !bluetooth_adapter_->HasObserver(this))
+    bluetooth_adapter_->AddObserver(this);
+}
+
+void ArcBluetoothBridge::OnInstanceClosed() {
+  if (bluetooth_adapter_)
+    bluetooth_adapter_->RemoveObserver(this);
 }
 
 void ArcBluetoothBridge::AdapterPoweredChanged(BluetoothAdapter* adapter,

components/arc/bluetooth/arc_bluetooth_bridge.h

@@ -45,6 +45,7 @@ class ArcBluetoothBridge
 
   // Overridden from InstanceHolder<mojom::BluetoothInstance>::Observer:
   void OnInstanceReady() override;
+  void OnInstanceClosed() override;
 
   void OnAdapterInitialized(scoped_refptr<device::BluetoothAdapter> adapter);
 

device/bluetooth/bluetooth_adapter.cc

@@ -55,6 +55,11 @@ void BluetoothAdapter::RemoveObserver(BluetoothAdapter::Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
+bool BluetoothAdapter::HasObserver(BluetoothAdapter::Observer* observer) {
+  DCHECK(observer);
+  return observers_.HasObserver(observer);
+}
+
 void BluetoothAdapter::StartDiscoverySession(
     const DiscoverySessionCallback& callback,
     const ErrorCallback& error_callback) {

device/bluetooth/bluetooth_adapter.h

@@ -272,6 +272,7 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapter
   // methods to determine which adapter is issuing the event.
   virtual void AddObserver(BluetoothAdapter::Observer* observer);
   virtual void RemoveObserver(BluetoothAdapter::Observer* observer);
+  virtual bool HasObserver(BluetoothAdapter::Observer* observer);
 
   // The address of this adapter. The address format is "XX:XX:XX:XX:XX:XX",
   // where each XX is a hexadecimal number.