[scheduler] Move TimeBudgetPool to a separate file.

third_party/WebKit/Source/platform/BUILD.gn

Index: third_party/WebKit/Source/platform/BUILD.gn
diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
index cb99486d682a62aa3b34d2a5d8f765ba10712d68..38c78c03ab872f1d23aa07c566672bacfbac7fc1 100644
--- a/third_party/WebKit/Source/platform/BUILD.gn
+++ b/third_party/WebKit/Source/platform/BUILD.gn
@@ -1201,6 +1201,8 @@ component("platform") {
     "scheduler/child/worker_scheduler_impl.h",
     "scheduler/renderer/auto_advancing_virtual_time_domain.cc",
     "scheduler/renderer/auto_advancing_virtual_time_domain.h",
+    "scheduler/renderer/budget_pool.cc",
+    "scheduler/renderer/budget_pool.h",
     "scheduler/renderer/deadline_task_runner.cc",
     "scheduler/renderer/deadline_task_runner.h",
     "scheduler/renderer/idle_time_estimator.cc",
@@ -1783,6 +1785,7 @@ test("blink_platform_unittests") {
     "scheduler/child/webthread_impl_for_worker_scheduler_unittest.cc",
     "scheduler/child/worker_scheduler_impl_unittest.cc",
     "scheduler/renderer/auto_advancing_virtual_time_domain_unittest.cc",
+    "scheduler/renderer/budget_pool_unittest.cc",
     "scheduler/renderer/deadline_task_runner_unittest.cc",
     "scheduler/renderer/idle_time_estimator_unittest.cc",
     "scheduler/renderer/renderer_scheduler_impl_unittest.cc",