Add TaskScheduler::InitParams and accept it in TaskSchedulerImpl constructor.

base/task_scheduler/task_scheduler.h

Index: base/task_scheduler/task_scheduler.h
diff --git a/base/task_scheduler/task_scheduler.h b/base/task_scheduler/task_scheduler.h
index 4b07c88998ba922f46914f7f88055b939e1947cc..a869858ffb921365ae82246675fa4a38cfcdf535 100644
--- a/base/task_scheduler/task_scheduler.h
+++ b/base/task_scheduler/task_scheduler.h
@@ -15,6 +15,7 @@
 #include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
 #include "base/task_runner.h"
+#include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/task_traits.h"
 #include "base/time/time.h"
 
@@ -29,7 +30,6 @@ class Location;
 namespace base {
 
 class HistogramBase;
-class SchedulerWorkerPoolParams;
 
 // Interface for a task scheduler and static methods to manage the instance used
 // by the post_task.h API. Note: all base/task_scheduler users should go through
@@ -37,6 +37,22 @@ class SchedulerWorkerPoolParams;
 // which manages the process' instance.
 class BASE_EXPORT TaskScheduler {
  public:
+  struct BASE_EXPORT InitParams {
+    InitParams(
+        const SchedulerWorkerPoolParams& background_worker_pool_params_in,
+        const SchedulerWorkerPoolParams&
+            background_blocking_worker_pool_params_in,
+        const SchedulerWorkerPoolParams& foreground_worker_pool_params_in,
+        const SchedulerWorkerPoolParams&
+            foreground_blocking_worker_pool_params_in);
+    ~InitParams();
+
+    const SchedulerWorkerPoolParams background_worker_pool_params;
+    const SchedulerWorkerPoolParams background_blocking_worker_pool_params;
+    const SchedulerWorkerPoolParams foreground_worker_pool_params;
+    const SchedulerWorkerPoolParams foreground_blocking_worker_pool_params;
+  };
+
   // Returns the index of the worker pool in which a task with |traits| should
   // run. This should be coded in a future-proof way: new traits should
   // gracefully map to a default pool.
@@ -121,11 +137,24 @@ class BASE_EXPORT TaskScheduler {
   // |worker_pool_index_for_traits_callback| returns the index in |worker_pools|
   // of the worker pool in which a task with given traits should run. For tests,
   // prefer base::test::ScopedTaskScheduler (ensures isolation).
+  //
+  // Deprecated. Use the overload below instead. https://crbug.com/690706
   static void CreateAndSetDefaultTaskScheduler(
       const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector,
       const WorkerPoolIndexForTraitsCallback&
           worker_pool_index_for_traits_callback);
 
+  // Creates and sets a task scheduler using custom params. |name| is used to
+  // label threads and histograms. It should identify the component that creates
+  // the TaskScheduler. |init_params| is used to initialize the worker pools.
+  // CHECKs on failure. For tests, prefer base::test::ScopedTaskScheduler
+  // (ensures isolation).
+  //
+  // Note: The names and priority hints in |init_params| are ignored (ref. TODO
+  // to remove them).
+  static void CreateAndSetDefaultTaskScheduler(const std::string& name,
+                                               const InitParams& init_params);
+
   // Registers |task_scheduler| to handle tasks posted through the post_task.h
   // API for this process. For tests, prefer base::test::ScopedTaskScheduler
   // (ensures isolation).