Runtime checks so that CoreBluetooth only used on >= 10.10

device/bluetooth/bluetooth_adapter_mac_unittest.mm

Index: device/bluetooth/bluetooth_adapter_mac_unittest.mm
diff --git a/device/bluetooth/bluetooth_adapter_mac_unittest.mm b/device/bluetooth/bluetooth_adapter_mac_unittest.mm
index 3e7ab6832ede2641ba91284e7597cdc009d3560b..ee01cd67b30c8fd29274a4b44f4500e2ed9f6be0 100644
--- a/device/bluetooth/bluetooth_adapter_mac_unittest.mm
+++ b/device/bluetooth/bluetooth_adapter_mac_unittest.mm
@@ -25,9 +25,8 @@ class BluetoothAdapterMacTest : public testing::Test {
 
   // Helper methods for setup and access to BluetoothAdapterMacTest's members.
   bool SetMockCentralManager() {
-    Class aClass = NSClassFromString(@"CBCentralManager");
-    if (aClass == nil) {
-      LOG(WARNING) << "CoreBluetooth not available, skipping unit test.";
+    if (!BluetoothAdapterMac::IsLowEnergyAvailable()) {
+      LOG(WARNING) << "Low Energy Bluetooth unavailable, skipping unit test.";
       return false;
     }
     mock_central_manager_ = [[MockCentralManager alloc] init];