Control TaskScheduler initialization params in renderers via field trial.

components/task_scheduler_util/renderer/initialization.h

Index: components/task_scheduler_util/renderer/initialization.h
diff --git a/components/task_scheduler_util/renderer/initialization.h b/components/task_scheduler_util/renderer/initialization.h
new file mode 100644
index 0000000000000000000000000000000000000000..6f351507eec4904cc16a47cb029ef7ac86328671
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+++ b/components/task_scheduler_util/renderer/initialization.h
@@ -0,0 +1,32 @@
+// Copyright 2017 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_RENDERER_INITIALIZATION_H_
+#define COMPONENTS_TASK_SCHEDULER_UTIL_RENDERER_INITIALIZATION_H_
+
+#include <stddef.h>
+
+#include <vector>
+
+#include "base/task_scheduler/scheduler_worker_pool_params.h"
+
+namespace base {
+class TaskTraits;
+}
+
+namespace task_scheduler_util {
+
+// Gets a vector of SchedulerWorkerPoolParams to initialize TaskScheduler in a
+// renderer based off variation params specified on the command line. Returns an
+// empty vector if variation params specified on the command line are incomplete
+// or invalid.
+std::vector<base::SchedulerWorkerPoolParams> GetRendererWorkerPoolParams();
+
+// Maps |traits| to the index of a renderer worker pool vector provided by
+// GetRendererWorkerPoolParams().
+size_t RendererWorkerPoolIndexForTraits(const base::TaskTraits& traits);
+
+}  // namespace task_scheduler_util
+
+#endif  // COMPONENTS_TASK_SCHEDULER_UTIL_RENDERER_INITIALIZATION_H_