Add Browser Task Scheduler Flags to iOS

ios/chrome/browser/about_flags.mm

 // Copyright 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.
 
 // Implementation of about_flags for iOS that sets flags based on experimental
 // settings.
 
 #include "ios/chrome/browser/about_flags.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #import <UIKit/UIKit.h>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/sys_info.h"
+#include "base/task_scheduler/switches.h"
 #include "components/dom_distiller/core/dom_distiller_switches.h"
 #include "components/flags_ui/feature_entry.h"
 #include "components/flags_ui/feature_entry_macros.h"
 #include "components/flags_ui/flags_storage.h"
 #include "components/flags_ui/flags_ui_switches.h"
 #include "components/strings/grit/components_strings.h"
 #include "components/sync/driver/sync_driver_switches.h"
 #include "google_apis/gaia/gaia_switches.h"
 #include "ios/chrome/browser/chrome_switches.h"
 #include "ios/chrome/grit/ios_strings.h"
@@ skipping 18 matching lines @@
 // When adding a new choice, add it to the end of the list.
 const flags_ui::FeatureEntry kFeatureEntries[] = {
     {"contextual-search", IDS_IOS_FLAGS_CONTEXTUAL_SEARCH,
      IDS_IOS_FLAGS_CONTEXTUAL_SEARCH_DESCRIPTION, flags_ui::kOsIos,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableContextualSearch,
                                switches::kDisableContextualSearch)},
     {"ios-physical-web", IDS_IOS_FLAGS_PHYSICAL_WEB,
      IDS_IOS_FLAGS_PHYSICAL_WEB_DESCRIPTION, flags_ui::kOsIos,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableIOSPhysicalWeb,
                                switches::kDisableIOSPhysicalWeb)},
+    {"browser-task-scheduler", IDS_FLAGS_BROWSER_TASK_SCHEDULER_NAME,

[rohitrao (ping after 24h), 2016/10/25 12:07:07]

Are you simply this to maintain consistency with desktop, or do you expect users
to flip this flag?

We only expose a limited set of flags on iOS, and I need to get clarification on
how we decide what makes the cut.  I'll find out today.

[robliao, 2016/10/26 17:28:19]

Users that plan on opting into the task scheduler all the time will flip this
flag. Since our deployment is going through Finch, there's no easy way to force
enable this feature on iOS for issue repros.

+     IDS_FLAGS_BROWSER_TASK_SCHEDULER_DESCRIPTION, flags_ui::kOsIos,
+     ENABLE_DISABLE_VALUE_TYPE(switches::kEnableBrowserTaskScheduler,
+                               switches::kDisableBrowserTaskScheduler)},
 };
 
 // Add all switches from experimental flags to |command_line|.
 void AppendSwitchesFromExperimentalSettings(base::CommandLine* command_line) {
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
 
   // GAIA staging environment.
   NSString* kGAIAEnvironment = @"GAIAEnvironment";
   NSString* gaia_environment = [defaults stringForKey:kGAIAEnvironment];
   if ([gaia_environment isEqualToString:@"Staging"]) {
@@ skipping 235 matching lines @@
 }
 
 namespace testing {
 
 const flags_ui::FeatureEntry* GetFeatureEntries(size_t* count) {
   *count = arraysize(kFeatureEntries);
   return kFeatureEntries;
 }
 
 }  // namespace testing