Clean up HID backend and API.

device/hid/hid_utils_mac.cc

-// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// 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_utils_mac.h"
 
-#include "base/basictypes.h"
-#include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 
-#if defined(OS_MACOSX)
-#include <CoreFoundation/CoreFoundation.h>
-#include <IOKit/hid/IOHIDManager.h>
-#endif
-
 namespace device {
 
-bool GetHidIntProperty(IOHIDDeviceRef device,
-                       CFStringRef key,
-                       int32_t* result) {
+int32_t GetHidIntProperty(IOHIDDeviceRef device, CFStringRef key) {
+  int32_t value;
+  if (TryGetHidIntProperty(device, key, &value))
+    return value;
+  return 0;
+}
+
+std::string GetHidStringProperty(IOHIDDeviceRef device, CFStringRef key) {
+  std::string value;
+  TryGetHidStringProperty(device, key, &value);
+  return value;
+}
+
+bool TryGetHidIntProperty(IOHIDDeviceRef device,
+                          CFStringRef key,
+                          int32_t* result) {
   CFNumberRef ref = base::mac::CFCast<CFNumberRef>(
       IOHIDDeviceGetProperty(device, key));
   return ref && CFNumberGetValue(ref, kCFNumberSInt32Type, result);
 }
 
-bool GetHidStringProperty(IOHIDDeviceRef device,
-                          CFStringRef key,
-                          std::string* result) {
+bool TryGetHidStringProperty(IOHIDDeviceRef device,
+                             CFStringRef key,
+                             std::string* result) {
   CFStringRef ref = base::mac::CFCast<CFStringRef>(
       IOHIDDeviceGetProperty(device, key));
   if (!ref) {
     return false;
   }
   *result = base::SysCFStringRefToUTF8(ref);
   return true;
 }
 
 }  // namespace device