Add Browser Task Scheduler Flags to iOS

ios/chrome/browser/about_flags.mm

Index: ios/chrome/browser/about_flags.mm
diff --git a/ios/chrome/browser/about_flags.mm b/ios/chrome/browser/about_flags.mm
index 515fc1b2f51c990c3b80e74c1e1e9b49d6f66da2..e2ffb7fd9c3dda76830859ef23cdb0a1911d549a 100644
--- a/ios/chrome/browser/about_flags.mm
+++ b/ios/chrome/browser/about_flags.mm
@@ -19,6 +19,7 @@
 #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"
@@ -57,6 +58,10 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
      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|.