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..1f0a8f94a9d94abf09e280b6ff22750b9ef18739 100644
--- a/device/bluetooth/bluetooth_adapter_mac_unittest.mm
+++ b/device/bluetooth/bluetooth_adapter_mac_unittest.mm
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/mac/mac_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/test/test_simple_task_runner.h"
 #include "device/bluetooth/bluetooth_adapter.h"
@@ -25,9 +26,10 @@ 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 (!base::mac::IsOSYosemiteOrLater()) {
+      // For stability we only use CoreBluetooth on OS X >= 10.10.  Thus on
+      // previous OS X versions the code cannot be tested.
+      LOG(WARNING) << "OS X version < 10.10, skipping unit test.";
       return false;
     }
     mock_central_manager_ = [[MockCentralManager alloc] init];