Do not use the 'original' profile for guest sessions

For guest sessions (profile->IsGuestSession), we do not use
profile->GetOriginalProfile() for browser windows, we use the off the
record profile instead.

This was triggering an assert at the top of Browser::Browser().

BUG=434491

Review URL: https://codereview.chromium.org/741883002

Cr-Commit-Position: refs/heads/master@{#305053}

chrome/browser/ui/settings_window_manager.cc

@@ -35,8 +35,11 @@ void SettingsWindowManager::RemoveObserver(
 
 void SettingsWindowManager::ShowChromePageForProfile(Profile* profile,
                                                      const GURL& gurl) {
-  // Use the original (non off-the-record) profile for settings.
-  profile = profile->GetOriginalProfile();
+  // Use the original (non off-the-record) profile for settings unless
+  // this is a guest session.
+  if (!profile->IsGuestSession() && profile->IsOffTheRecord())
+    profile = profile->GetOriginalProfile();
+
   // Look for an existing browser window.
   Browser* browser = FindBrowserForProfile(profile);
   if (browser) {