Optimize ShouldLaunchIncognito() since its on the startup path.

chrome/browser/prefs/incognito_mode_prefs.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prefs/incognito_mode_prefs.h"
 
 #include <stdint.h>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 124 matching lines @@
     *out_value = ENABLED;
     return false;
   }
   *out_value = static_cast<Availability>(in_value);
   return true;
 }
 
 // static
 IncognitoModePrefs::Availability IncognitoModePrefs::GetAvailability(
     const PrefService* pref_service) {
-  DCHECK(pref_service);
-  int pref_value = pref_service->GetInteger(prefs::kIncognitoModeAvailability);
-  Availability result = IncognitoModePrefs::ENABLED;
-  bool valid = IntToAvailability(pref_value, &result);
-  DCHECK(valid);
-  if (ArePlatformParentalControlsEnabled()) {
-    if (result == IncognitoModePrefs::FORCED)
-      LOG(ERROR) << "Ignoring FORCED incognito. Parental control logging on";
-    return IncognitoModePrefs::DISABLED;
-  }
-  return result;
+  return GetAvailabilityInternal(pref_service, CHECK_PARENTAL_CONTROLS);
 }
 
 // static
 void IncognitoModePrefs::SetAvailability(PrefService* prefs,
                                          const Availability availability) {
   prefs->SetInteger(prefs::kIncognitoModeAvailability, availability);
 }
 
 // static
 void IncognitoModePrefs::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterIntegerPref(prefs::kIncognitoModeAvailability,
                                 IncognitoModePrefs::ENABLED);
 }
 
 // static
 bool IncognitoModePrefs::ShouldLaunchIncognito(
     const base::CommandLine& command_line,
     const PrefService* prefs) {
-  Availability incognito_avail = GetAvailability(prefs);
-  return incognito_avail != IncognitoModePrefs::DISABLED &&
-         (command_line.HasSwitch(switches::kIncognito) ||
-          incognito_avail == IncognitoModePrefs::FORCED);
+  // Note: We only absolutely need to check for parental controls in the
+  // startup path if the user requested to launch in incognito mode or
+  // it was forced via prefs, since computing parental controls can be

[gab, 2016/10/03 17:08:12]

We need to check parental controls (...) since parentals controls can be slow?

Don't think that's what you intended to say here?

[Alexei Svitkine (slow), 2016/10/03 18:57:39]

I think the comment wording did work - "we only do X in certain cases since X
can be slow" is what it's saying, which is a valid phrasing.

However, I agree it was a bit run-on - so I've reworded so it's two sentences
now and easier to read.

+  // slow. Otherwise, we can check later.
+  bool should_use_incognito =

[gab, 2016/10/03 17:08:12]

const

[Alexei Svitkine (slow), 2016/10/03 18:57:39]

Done.

+      command_line.HasSwitch(switches::kIncognito) ||
+      GetAvailabilityInternal(prefs, DONT_CHECK_PARENTAL_CONTROLS) ==
+          IncognitoModePrefs::FORCED;
+  // Only check parental controls only if |should_use_incognito| is true.

[gab, 2016/10/03 17:08:12]

double "only"

This comment is also probably redundant (i.e. it's merely stating what the
simple code below it does word for word).

[Alexei Svitkine (slow), 2016/10/03 18:57:39]

Done. After re-wording the comment above, I'm OK with not having this extra
comment.

+  return should_use_incognito &&
+         GetAvailabilityInternal(prefs, CHECK_PARENTAL_CONTROLS) !=
+             IncognitoModePrefs::DISABLED;
 }
 
 // static
 bool IncognitoModePrefs::CanOpenBrowser(Profile* profile) {
   if (profile->IsGuestSession())
     return true;
 
   switch (GetAvailability(profile->GetPrefs())) {
     case IncognitoModePrefs::ENABLED:
       return true;
@@ skipping 24 matching lines @@
 bool IncognitoModePrefs::ArePlatformParentalControlsEnabled() {
 #if defined(OS_WIN)
   return PlatformParentalControlsValue::GetInstance()->is_enabled();
 #elif BUILDFLAG(ANDROID_JAVA_UI)
   return chrome::android::ChromeApplication::AreParentalControlsEnabled();
 #else
   return false;
 #endif
 }
 
+// static
+IncognitoModePrefs::Availability IncognitoModePrefs::GetAvailabilityInternal(
+    const PrefService* pref_service,
+    GetAvailabilityMode mode) {
+  DCHECK(pref_service);
+  int pref_value = pref_service->GetInteger(prefs::kIncognitoModeAvailability);
+  Availability result = IncognitoModePrefs::ENABLED;
+  bool valid = IntToAvailability(pref_value, &result);
+  DCHECK(valid);
+  if (result != IncognitoModePrefs::DISABLED &&
+      mode == CHECK_PARENTAL_CONTROLS && ArePlatformParentalControlsEnabled()) {
+    if (result == IncognitoModePrefs::FORCED)
+      LOG(ERROR) << "Ignoring FORCED incognito. Parental control logging on";
+    return IncognitoModePrefs::DISABLED;
+  }
+  return result;
+}