Enable profile switching for standalone App Launcher via the Settings App.

chrome/browser/profiles/profile_manager.cc

Index: chrome/browser/profiles/profile_manager.cc
diff --git a/chrome/browser/profiles/profile_manager.cc b/chrome/browser/profiles/profile_manager.cc
index 714c2883aa4fb51c8e8260838dcdd9d41b9d6c9c..ccf1b75cbb67458b2d7fc123abda39f856c8e81f 100644
--- a/chrome/browser/profiles/profile_manager.cc
+++ b/chrome/browser/profiles/profile_manager.cc
@@ -310,17 +310,21 @@ Profile* ProfileManager::GetLastUsedProfile(const FilePath& user_data_dir) {
     return GetDefaultProfile(user_data_dir);
 #endif
 
+  return GetProfile(GetLastUsedProfilePath(user_data_dir));
+}
+
+FilePath ProfileManager::GetLastUsedProfilePath(const FilePath& user_data_dir) {
   FilePath last_used_profile_dir(user_data_dir);
-  std::string last_profile_used;
+  std::string last_used_profile;
   PrefService* local_state = g_browser_process->local_state();
   DCHECK(local_state);
 
-  if (local_state->HasPrefPath(prefs::kProfileLastUsed))
-    last_profile_used = local_state->GetString(prefs::kProfileLastUsed);
-  last_used_profile_dir = last_profile_used.empty() ?
-      last_used_profile_dir.AppendASCII(chrome::kInitialProfile) :
-      last_used_profile_dir.AppendASCII(last_profile_used);
-  return GetProfile(last_used_profile_dir);
+  if (local_state->HasPrefPath(prefs::kProfileLastUsed)) {
+    return last_used_profile_dir.AppendASCII(
+        local_state->GetString(prefs::kProfileLastUsed));
+  }
+
+  return last_used_profile_dir.AppendASCII(chrome::kInitialProfile);
 }
 
 std::vector<Profile*> ProfileManager::GetLastOpenedProfiles(
@@ -840,6 +844,9 @@ void ProfileManager::CreateMultiProfileAsync(
 
 // static
 void ProfileManager::RegisterPrefs(PrefServiceSimple* prefs) {
+#if defined(ENABLE_APP_LIST)
+  prefs->RegisterStringPref(prefs::kAppListProfile, "");

[sail, 2013/01/23 16:55:24]

This should go in the app list code base. Not profiles. See
chrome::RegisterLocalState() for other people do this.

In general, keep your feature code in its own codebase.

[koz (OOO until 15th September), 2013/01/25 00:32:46]

Done.

+#endif
   prefs->RegisterStringPref(prefs::kProfileLastUsed, "");
   prefs->RegisterIntegerPref(prefs::kProfilesNumCreated, 1);
   prefs->RegisterListPref(prefs::kProfilesLastActive);
@@ -992,6 +999,18 @@ void ProfileManager::ScheduleProfileForDeletion(
     }
   }
 
+#if defined(ENABLE_APP_LIST)
+  // If the profile the app list uses just got deleted, reset it to the last
+  // used profile.
+  // TODO(koz): Manage the kAppListProfile preference not in this class.
+  std::string app_list_last_profile = local_state->GetString(

[sail, 2013/01/23 16:55:24]

same, don't put your feature code here
if you need to do something when a profile is deleted then do the same thing
everyone else does, listen for a notification

[koz (OOO until 15th September), 2013/01/25 00:32:46]

Done.

+      prefs::kAppListProfile);
+  if (profile_dir.BaseName().MaybeAsASCII() == app_list_last_profile) {
+    local_state->SetString(prefs::kAppListProfile,
+        local_state->GetString(prefs::kProfileLastUsed));
+  }
+#endif
+
   // TODO(sail): Due to bug 88586 we don't delete the profile instance. Once we
   // start deleting the profile instance we need to close background apps too.
   Profile* profile = GetProfileByPath(profile_dir);