Optimize ShouldLaunchIncognito() since its on the startup path.

chrome/browser/prefs/incognito_mode_prefs.h

Index: chrome/browser/prefs/incognito_mode_prefs.h
diff --git a/chrome/browser/prefs/incognito_mode_prefs.h b/chrome/browser/prefs/incognito_mode_prefs.h
index cbf30efa6abab726cdf420f57516228d7e370bda..2d02e089ec2d0f32518950916fca938c20907416 100644
--- a/chrome/browser/prefs/incognito_mode_prefs.h
+++ b/chrome/browser/prefs/incognito_mode_prefs.h
@@ -78,6 +78,18 @@ class IncognitoModePrefs {
   static bool ArePlatformParentalControlsEnabled() WARN_UNUSED_RESULT;
 
  private:
+  // Specifies whether parental controls should be checked. See comment below.
+  enum GetAvailabilityMode {
+    CHECK_PARENTAL_CONTROLS,
+    DONT_CHECK_PARENTAL_CONTROLS,
+  };
+
+  // Internal version of GetAvailability() that specifies whether parental
+  // controls should be checked (which is expensive and not always necessary
+  // to do - such as when checking for FORCED state).
+  static Availability GetAvailabilityInternal(const PrefService* pref_service,
+                                              GetAvailabilityMode mode);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncognitoModePrefs);
 };