chrome.bluetooth API improvements.

device/bluetooth/bluetooth_device_mac.mm

Index: device/bluetooth/bluetooth_device_mac.mm
diff --git a/device/bluetooth/bluetooth_device_mac.mm b/device/bluetooth/bluetooth_device_mac.mm
index 50762d2d3eaa1173ce52cb54f3fffeee427e6d72..f7f8a1276e4f1e59c3b7bbe7bd75b11f1ad1a524 100644
--- a/device/bluetooth/bluetooth_device_mac.mm
+++ b/device/bluetooth/bluetooth_device_mac.mm
@@ -36,6 +36,8 @@
 
 namespace {
 
+const char kFailedToConnect[] = "Connection failed";
+
 // Converts |uuid| to a IOBluetoothSDPUUID instance.
 //
 // |uuid| must be in the format of XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX.
@@ -214,14 +216,13 @@ void BluetoothDeviceMac::ConnectToService(
   }
 }
 
-void BluetoothDeviceMac::ConnectToProfile(
-    device::BluetoothProfile* profile,
-    const base::Closure& callback,
-    const ErrorCallback& error_callback) {
+void BluetoothDeviceMac::ConnectToProfile(BluetoothProfile* profile,
+                                          const base::Closure& callback,
+                                          const ErrorCallback& error_callback) {
   if (static_cast<BluetoothProfileMac*>(profile)->Connect(device_))
     callback.Run();
   else
-    error_callback.Run();
+    error_callback.Run(kFailedToConnect);
 }
 
 void BluetoothDeviceMac::SetOutOfBandPairingData(