Remove non-existing headers from the build

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 8c46633ac246637dc02cfba5808478dbc50a03ef..f48b6f619d8c1e04d9547d6b0e97fa62461fb58d 100644
--- a/third_party/WebKit/Source/platform/BUILD.gn
+++ b/third_party/WebKit/Source/platform/BUILD.gn
@@ -1274,6 +1274,7 @@ component("platform") {
     "scheduler/base/task_queue_manager_delegate.h",
     "scheduler/base/task_queue_selector.cc",
     "scheduler/base/task_queue_selector.h",
+    "scheduler/base/task_time_observer.h",
     "scheduler/base/thread_load_tracker.cc",
     "scheduler/base/thread_load_tracker.h",
     "scheduler/base/time_converter.h",
@@ -1297,6 +1298,7 @@ component("platform") {
     "scheduler/child/scheduler_tqm_delegate_impl.cc",
     "scheduler/child/scheduler_tqm_delegate_impl.h",
     "scheduler/child/single_thread_idle_task_runner.cc",
+    "scheduler/child/web_scheduler.h",
     "scheduler/child/web_scheduler_impl.cc",
     "scheduler/child/web_scheduler_impl.h",
     "scheduler/child/web_task_runner_impl.cc",
@@ -1336,6 +1338,7 @@ component("platform") {
     "scheduler/renderer/user_model.h",
     "scheduler/renderer/web_frame_scheduler_impl.cc",
     "scheduler/renderer/web_frame_scheduler_impl.h",
+    "scheduler/renderer/web_view_scheduler.h",
     "scheduler/renderer/web_view_scheduler_impl.cc",
     "scheduler/renderer/web_view_scheduler_impl.h",
     "scheduler/renderer/webthread_impl_for_renderer_scheduler.cc",