mac: Add metrics for AppKit Fullscreen style.

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics_mac.mm

+// 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 "chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h"
+
+#include "base/mac/sdk_forward_declarations.h"
+#include "base/metrics/histogram.h"
+
+namespace {
+
+// The possible values of the setting "Screens Have Separate Spaces".
+enum SeparateSpaces {

[Ilya Sherman, 2014/10/21 21:23:55]

nit: "SeparateSpaces" is a pretty odd type name.  One suggestion:
"ScreenSpacesConfiguration".

[erikchen, 2014/10/24 17:55:02]

Used your suggestion. Thanks!

+  SCREENS_CANNOT_HAVE_SEPARATE_SPACES = 0,
+  SCREENS_HAVE_SEPARATE_SPACES = 1,
+  SCREENS_HAVE_SHARED_SPACES = 2,
+  SEPARATE_SPACES_COUNT = 3
+};
+
+}  // namespace
+
+void ChromeBrowserMainExtraPartsMetrics::RecordMacMetrics() {
+  int separate_spaces = SCREENS_CANNOT_HAVE_SEPARATE_SPACES;

[Ilya Sherman, 2014/10/21 21:23:55]

nit: Why is this an int, rather than a "SeparateSpaces"?

[erikchen, 2014/10/24 17:55:02]

No good reason. Fixed.

+
+  if ([NSScreen respondsToSelector:@selector(screensHaveSeparateSpaces)]) {
+    BOOL screens_have_separate_spaces = [NSScreen screensHaveSeparateSpaces];
+    separate_spaces = screens_have_separate_spaces
+                          ? SCREENS_HAVE_SEPARATE_SPACES
+                          : SCREENS_HAVE_SHARED_SPACES;
+  }
+  UMA_HISTOGRAM_ENUMERATION("OSX.Settings.ScreensHaveSeparateSpaces",
+                            separate_spaces,
+                            SEPARATE_SPACES_COUNT);
+}