mac: Add metrics to record Bluetooth availability and capabilities.

chrome/browser/mac/hardware_utility.h

+// 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.
+
+#ifndef CHROME_BROWSER_MAC_HARDWARE_UTILITY_H_
+#define CHROME_BROWSER_MAC_HARDWARE_UTILITY_H_
+
+namespace hardware_utility {
+
+// The enum is used in a histogram, so the values must not change.
+enum BluetoothAvailability {
+  BLUETOOTH_NOT_AVAILABLE = 0,

[Mark Mentovai, 2014/07/09 17:53:00]

The = 0 is fine here, but just let the compiler count out the rest of the
constants for you.

[erikchen, 2014/07/09 20:14:42]

The Google C++ style guide allows for both styles, and I prefer this one here
since the actual numerical values matter (there are matching values in
histograms.xml). This makes it less likely that someone will accidentally change
the order or insert a new enum value at the wrong location.

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Enumerator_Names

+  BLUETOOTH_AVAILABLE_WITHOUT_LE = 1,
+  BLUETOOTH_AVAILABLE_WITH_LE = 2,
+  BLUETOOTH_AVAILABILITY_ERROR = 3,
+  BLUETOOTH_AVAILABILITY_COUNT,
+};
+
+// Returns the bluetooth availability of the system's hardware.
+BluetoothAvailability GetBluetoothAvailability();
+
+}  // namespace hardware_utility
+
+#endif  // CHROME_BROWSER_MAC_HARDWARE_UTILITY_H_