HID report descriptors not available before OS X 10.8.

device/hid/hid_service_mac.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "device/hid/hid_service_mac.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #include <IOKit/hid/IOHIDDevice.h>
 
 #include <set>
@@ skipping 236 matching lines @@
   base::ScopedCFTypeRef<IOHIDDeviceRef> hid_device(
       IOHIDDeviceCreate(kCFAllocatorDefault, service));
   if (!hid_device) {
     HID_LOG(EVENT) << "Unable to create IOHIDDevice object for new device.";
     return nullptr;
   }
 
   std::vector<uint8> report_descriptor;
   if (!TryGetHidDataProperty(hid_device, CFSTR(kIOHIDReportDescriptorKey),
                              &report_descriptor)) {
-    HID_LOG(EVENT) << "Unable to get report descriptor for new device.";
-    return nullptr;
+    HID_LOG(DEBUG) << "Device report descriptor not available.";
   }
 
   return new HidDeviceInfo(
       entry_id, GetHidIntProperty(hid_device, CFSTR(kIOHIDVendorIDKey)),
       GetHidIntProperty(hid_device, CFSTR(kIOHIDProductIDKey)),
       GetHidStringProperty(hid_device, CFSTR(kIOHIDProductKey)),
       GetHidStringProperty(hid_device, CFSTR(kIOHIDSerialNumberKey)),
       kHIDBusTypeUSB,  // TODO(reillyg): Detect Bluetooth. crbug.com/443335
       report_descriptor);
 }
 
 }  // namespace device