Adding show profile switcher field trial.

chrome/browser/profiles/profile_manager.h

Index: chrome/browser/profiles/profile_manager.h
diff --git a/chrome/browser/profiles/profile_manager.h b/chrome/browser/profiles/profile_manager.h
index 9d1e03f7be98e6f2588722ed9ca352026de91515..8a45c22ace68f7266d67b370803f4e2dd9d6870a 100644
--- a/chrome/browser/profiles/profile_manager.h
+++ b/chrome/browser/profiles/profile_manager.h
@@ -202,6 +202,13 @@ class ProfileManager : public base::NonThreadSafe,
   // Checks if multiple profiles is enabled.
   static bool IsMultipleProfilesEnabled();
 
+  // Force IsMultipleProfilesEnabled to return a given value. For testing
+  // purposes.
+  static void ForceMultipleProfilesForTests(bool forcedValue);
+
+  // Lets IsMultipleProfilesEnabled behave in a normal, unforced way.
+  static void UnforceMultipleProfilesForTests();
+
   // Autoloads profiles if they are running background apps.
   void AutoloadProfiles();
 
@@ -349,6 +356,14 @@ class ProfileManager : public base::NonThreadSafe,
   std::vector<Profile*> active_profiles_;
   bool closing_all_browsers_;
 
+  // For forcing IsMultiProfilesEnabled to the value of
+  // multiple_profiles_forced_value_. Used for testing.
+  static bool is_multiple_profiles_forced_;

[sail, 2013/01/31 17:15:23]

maybe use an enum instead of 2 bools, something like
  default
  force_on
  force_off

[jwd, 2013/01/31 19:26:11]

Done. Kept the api the same though.

+
+  // The value returned by IsMultiProfilesEnabled when it's been forced. Used
+  // for testing.
+  static bool multiple_profiles_forced_value_;
+
   DISALLOW_COPY_AND_ASSIGN(ProfileManager);
 };