mac: Add metrics for AppKit Fullscreen style.

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h

Index: chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
diff --git a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
index 04f3f0e1f3008fa24599288113abd9565c1a82c0..74c31e3d83faa0834f9f3ac5079fb173c0072482 100644
--- a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
+++ b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
@@ -27,6 +27,11 @@ class ChromeBrowserMainExtraPartsMetrics : public ChromeBrowserMainExtraParts {
   virtual void PostBrowserStart() override;
 
  private:
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  // Records Mac specific metrics.
+  void RecordMacMetrics();
+#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
+
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainExtraPartsMetrics);
 };