Remove external begin frame source parameter and settings

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 2b62163b3443e4ebecd2b278a8bc716ace58d2f2..8c59725b8ff801ecbda7a3624f748cc8b772cb2f 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -183,8 +183,6 @@ Compositor::Compositor(ui::ContextFactory* context_factory,
   // thread.
   settings.image_decode_tasks_enabled = false;
 
-  settings.use_compositor_frame_sink_begin_frame_source = true;
-
   settings.gpu_memory_policy.bytes_limit_when_visible = 512 * 1024 * 1024;
   settings.gpu_memory_policy.priority_cutoff_when_visible =
       gpu::MemoryAllocation::CUTOFF_ALLOW_NICE_TO_HAVE;