Enable Initialization of the Task Scheduler by Default in the Browser Process

chrome/browser/chrome_browser_main.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/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <map>
@@ skipping 297 matching lines @@
 void AddFirstRunNewTabs(StartupBrowserCreator* browser_creator,
                         const std::vector<GURL>& new_tabs) {
   for (std::vector<GURL>::const_iterator it = new_tabs.begin();
        it != new_tabs.end(); ++it) {
     if (it->is_valid())
       browser_creator->AddFirstRunTab(*it);
   }
 }
 #endif  // !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 
 void MaybeInitializeTaskScheduler() {

[fdoray, 2016/11/15 18:40:17]

No Maybe

[robliao, 2016/11/16 19:04:17]

Done.

+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableBrowserTaskScheduler)) {
+    return;
+  }

[fdoray, 2016/11/15 18:40:16]

To migrate WorkerPool call sites, TaskScheduler must always be initialized. Can
you always initialize TaskScheduler and re-purpose this flag to enable/disable
redirection only? You'll need to update
IDS_FLAGS_BROWSER_TASK_SCHEDULER_DESCRIPTION.

[gab, 2016/11/15 20:40:33]

Agreed, can't ever have a disabled scheduler.

As discussed offline, update definition, but don't change flag name to avoid
toggling people that already use it off of it.

[robliao, 2016/11/16 19:04:17]

Done.

[robliao, 2016/11/16 19:04:17]

Done.

+
   static constexpr char kFieldTrialName[] = "BrowserScheduler";
   std::map<std::string, std::string> variation_params;
   if (!variations::GetVariationParams(kFieldTrialName, &variation_params)) {
-    DCHECK(!base::CommandLine::ForCurrentProcess()->HasSwitch(
-        switches::kEnableBrowserTaskScheduler))
-        << "The Browser Task Scheduler remains disabled with "
-        << switches::kEnableBrowserTaskScheduler
-        << " because there is no available variation param for this build or "
-           " the task scheduler is disabled in chrome://flags.";
-    return;
+    variation_params["Background"] = "3;8;0.1;0;30000";
+    variation_params["BackgroundFileIO"] = "3;8;0.1;0;30000";
+    variation_params["Foreground"] = "8;32;0.3;0;30000";
+    variation_params["ForegroundFileIO"] = "8;32;0.3;0;30000";

[fdoray, 2016/11/15 18:40:16]

To avoid duplication between iOS and other platforms, could you move these
values to components/task_scheduler_util/initialization_util.cc? You could fall
back on default values when some params are missing/invalid. You could even
support a combination of default values and field trial values.

[gab, 2016/11/15 20:40:33]

Need different defaults for OS_ANDROID too to match current Finch config.

Also, it's weird that c/task_scheduler_util/initialization_util.cc is browser
process specific. Can we find a more browser-specific name?

[robliao, 2016/11/16 19:04:17]

That's a natural result of the content DEPS restriction. Added Browser to the
function name.

[robliao, 2016/11/16 19:04:17]

If some params are missing and invalid, we probably want to just use the default
ones wholesale. Merging two configurations could lead to an unexpected
configuration combination.

As for where this lives, it's possible that we would use different values for
iOS, and so we would have to split it out in the future, so keeping it separate
seems reasonable for now. If we find values converging, then we can consider
centralizing.

   }
 
   if (!task_scheduler_util::InitializeDefaultTaskScheduler(variation_params))
     return;
 
   // TODO(gab): Remove this when http://crbug.com/622400 concludes.
   const auto sequenced_worker_pool_param =
       variation_params.find("RedirectSequencedWorkerPools");
   if (sequenced_worker_pool_param != variation_params.end() &&
       sequenced_worker_pool_param->second == "true") {
@@ skipping 1781 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }