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 e07df34dd28eb102c4e0c9a8098584e331c11c7e..076123e3ad8f97c08461aead83370581cf8bed54 100644
--- a/device/bluetooth/bluetooth_discovery_session.cc
+++ b/device/bluetooth/bluetooth_discovery_session.cc
@@ -9,13 +9,23 @@
 
 namespace device {
 
-BluetoothDiscoverySession::BluetoothDiscoverySession(BluetoothAdapter* adapter)
+BluetoothDiscoverySession::BluetoothDiscoverySession(
+    scoped_refptr<BluetoothAdapter> adapter)
     : active_(true),
       adapter_(adapter),
       weak_ptr_factory_(this) {
+  DCHECK(adapter_.get());
+}
+
+BluetoothDiscoverySession::BluetoothDiscoverySession()
+    : active_(false),
+      weak_ptr_factory_(this) {
 }
 
 BluetoothDiscoverySession::~BluetoothDiscoverySession() {
+  if (!active_)
+    return;
+  DCHECK(adapter_.get());
   Stop(base::Bind(&base::DoNothing), base::Bind(&base::DoNothing));
   adapter_->DiscoverySessionDestroyed(this);
 }
@@ -28,11 +38,12 @@ 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(),