scheduler: Always create a real scheduler in unit tests

components/scheduler/BUILD.gn

Index: components/scheduler/BUILD.gn
diff --git a/components/scheduler/BUILD.gn b/components/scheduler/BUILD.gn
index f55b542fe95c14f14222b5dd450e6e02baf30740..587516f3ecb5ee4525f627a2bb0e538593fac3db 100644
--- a/components/scheduler/BUILD.gn
+++ b/components/scheduler/BUILD.gn
@@ -60,3 +60,14 @@ source_set("unit_tests") {
     "//testing/gtest",
   ]
 }
+
+# GYP version: components/scheduler.gypi:scheduler_test_support
+static_library("test_support") {
+  sources = rebase_path(scheduler_gypi_values.scheduler_test_support_sources,
+                        ".",
+                        "//components/scheduler")
+
+  deps = [
+    "//base",
+  ]
+}