Remove external begin frame source parameter and settings

cc/trees/remote_channel_main.cc

Index: cc/trees/remote_channel_main.cc
diff --git a/cc/trees/remote_channel_main.cc b/cc/trees/remote_channel_main.cc
index 7ce6fd1efc01a75b27deef442857a05c3612dfb3..6b490697a0419208e0a9533d4a6503774aecad78 100644
--- a/cc/trees/remote_channel_main.cc
+++ b/cc/trees/remote_channel_main.cc
@@ -219,8 +219,7 @@ void RemoteChannelMain::NotifyReadyToCommitOnImpl(
 }
 
 void RemoteChannelMain::SynchronouslyInitializeImpl(
-    LayerTreeHostInProcess* layer_tree_host,
-    std::unique_ptr<BeginFrameSource> external_begin_frame_source) {
+    LayerTreeHostInProcess* layer_tree_host) {
   TRACE_EVENT0("cc.remote", "RemoteChannelMain::SynchronouslyInitializeImpl");
   DCHECK(!initialized_);