Control TaskScheduler initialization params in renderers via field trial.

components/task_scheduler_util/common/variations_util.h

 // Copyright 2016 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.
 
 #ifndef COMPONENTS_TASK_SCHEDULER_UTIL_COMMON_VARIATIONS_UTIL_H_
 #define COMPONENTS_TASK_SCHEDULER_UTIL_COMMON_VARIATIONS_UTIL_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
+#include "base/strings/string_piece.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/threading/platform_thread.h"
 
+namespace base {
+class CommandLine;
+}
+
 namespace task_scheduler_util {
 
 class SchedulerImmutableWorkerPoolParams {
  public:
   SchedulerImmutableWorkerPoolParams(const char* name,
                                      base::ThreadPriority priority_hint);
 
   const char* name() const { return name_; }
   base::ThreadPriority priority_hint() const { return priority_hint_; }
 
  private:
   const char* name_;
   base::ThreadPriority priority_hint_;
 };
 
 // Returns a SchedulerWorkerPoolParams vector to initialize pools specified in
 // |constant_worker_pool_params_vector|. SchedulerWorkerPoolParams members
 // without a counterpart in SchedulerImmutableWorkerPoolParams are initialized
 // based of |variation_params|. Returns an empty vector on failure.
 std::vector<base::SchedulerWorkerPoolParams> GetWorkerPoolParams(
     const std::vector<SchedulerImmutableWorkerPoolParams>&
         constant_worker_pool_params_vector,
     const std::map<std::string, std::string>& variation_params);
 
+// Serializes variation params from the BrowserScheduler field trial whose key
+// start with |prefix| to the --task-scheduler-variation-params switch of
+// |command_line|.
+void AddVariationParamsToCommandLine(base::StringPiece key_prefix,
+                                     base::CommandLine* command_line);
+
+// Returns a map of key-value pairs deserialized from the
+// --task-scheduler-variation-params switch of |command_line|.
+std::map<std::string, std::string> GetVariationParamsFromCommandLine(
+    const base::CommandLine& command_line);
+
 }  // namespace task_scheduler_util
 
 #endif  // COMPONENTS_TASK_SCHEDULER_UTIL_COMMON_VARIATIONS_UTIL_H_