[BrowserSwitcher] Add Mac OS support

This enables the build on Mac OS X, and refactors
AlternativeBrowserDriver to work correctly on Mac OS.

Bug: 881589
Change-Id: I6e73d33d83af5bc1c0d8bb3ec3e76fcf8409ee2e
Reviewed-on: https://chromium-review.googlesource.com/c/1283835
Reviewed-by: Julian Pastarmov <[email protected]>
Reviewed-by: Gabriel Charette <[email protected]>
Commit-Queue: Nicolas Ouellet-Payeur <[email protected]>
Cr-Commit-Position: refs/heads/master@{#601570}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index d9fb637f..be3fc5c8 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -311,7 +311,8 @@
 #include "chrome/browser/ui/desktop_ios_promotion/desktop_ios_promotion_util.h"
 #endif
 
-#if defined(OS_WIN) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+#if defined(OS_WIN) || defined(OS_MACOSX) || \
+    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
 #include "chrome/browser/browser_switcher/browser_switcher_prefs.h"
 #endif
 
@@ -743,7 +744,8 @@
   safe_browsing::PostCleanupSettingsResetter::RegisterProfilePrefs(registry);
 #endif
 
-#if defined(OS_WIN) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+#if defined(OS_WIN) || defined(OS_MACOSX) || \
+    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
   browser_switcher::prefs::RegisterProfilePrefs(registry);
 #endif