Add a simple scheduler for animation frames

mc/scheduler/BUILD.gn

 # Copyright 2014 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.
 
-source_set("clock") {
+static_library("scheduler") {
+  sources = [
+    "scheduler.cc",
+    "scheduler.h",
+    "time_interval.cc",
+    "time_interval.h",
+    "timer.cc",
+    "timer.h",
+  ]
+
   deps = [
     "//base",
-    "//gin",
-    "//mojo/edk/js",
-    "//v8",
-  ]
-
-  sources = [
-    "monotonic_clock.cc",
-    "monotonic_clock.h",
   ]
 }