Migrate chrome.bluetooth API backend to use device::BluetoothDiscoverySession.

device/bluetooth/bluetooth_discovery_session.cc

Index: device/bluetooth/bluetooth_discovery_session.cc
diff --git a/device/bluetooth/bluetooth_discovery_session.cc b/device/bluetooth/bluetooth_discovery_session.cc
index afeacff7d48a2b640eaf767c925b44e49366b09d..7885e8697f2bc407a4087b763398779d8a2f90d6 100644
--- a/device/bluetooth/bluetooth_discovery_session.cc
+++ b/device/bluetooth/bluetooth_discovery_session.cc
@@ -9,7 +9,8 @@
 
 namespace device {
 
-BluetoothDiscoverySession::BluetoothDiscoverySession(BluetoothAdapter* adapter)
+BluetoothDiscoverySession::BluetoothDiscoverySession(
+    scoped_refptr<BluetoothAdapter> adapter)
     : active_(true),
       adapter_(adapter),
       weak_ptr_factory_(this) {
@@ -17,6 +18,7 @@ BluetoothDiscoverySession::BluetoothDiscoverySession(BluetoothAdapter* adapter)
 
 BluetoothDiscoverySession::~BluetoothDiscoverySession() {
   Stop(base::Bind(&base::DoNothing), base::Bind(&base::DoNothing));
+  DCHECK(adapter_.get());
   adapter_->DiscoverySessionDestroyed(this);
 }
 
@@ -24,11 +26,12 @@ void BluetoothDiscoverySession::Stop(
     const base::Closure& callback,
     const ErrorCallback& error_callback) {
   if (!active_) {
-    LOG(ERROR) << "Discovery session not active. Cannot stop.";
+    LOG(WARNING) << "Discovery session not active. Cannot stop.";
     error_callback.Run();
     return;
   }
   VLOG(1) << "Stopping device discovery session.";
+  DCHECK(adapter_.get());
   adapter_->RemoveDiscoverySession(
       base::Bind(&BluetoothDiscoverySession::OnStop,
                  weak_ptr_factory_.GetWeakPtr(),