Remove external begin frame source parameter and settings

cc/trees/proxy_main.cc

 // Copyright 2015 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.
 
 #include "cc/trees/proxy_main.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/trace_event/trace_event.h"
@@ skipping 331 matching lines @@
 bool ProxyMain::BeginMainFrameRequested() const {
   DCHECK(IsMainThread());
   return max_requested_pipeline_stage_ != NO_PIPELINE_STAGE;
 }
 
 void ProxyMain::MainThreadHasStoppedFlinging() {
   DCHECK(IsMainThread());
   channel_main_->MainThreadHasStoppedFlingingOnImpl();
 }
 
-void ProxyMain::Start(
-    std::unique_ptr<BeginFrameSource> external_begin_frame_source) {
+void ProxyMain::Start() {
   DCHECK(IsMainThread());
   DCHECK(layer_tree_host_->IsThreaded() || layer_tree_host_->IsRemoteServer());
   DCHECK(channel_main_);
-  DCHECK(!layer_tree_host_->GetSettings().use_external_begin_frame_source ||
-         external_begin_frame_source);
 
   // Create LayerTreeHostImpl.
-  channel_main_->SynchronouslyInitializeImpl(
-      layer_tree_host_, std::move(external_begin_frame_source));
+  channel_main_->SynchronouslyInitializeImpl(layer_tree_host_);
 
   started_ = true;
 }
 
 void ProxyMain::Stop() {
   TRACE_EVENT0("cc", "ProxyMain::Stop");
   DCHECK(IsMainThread());
   DCHECK(started_);
 
   channel_main_->SynchronouslyCloseImpl();
@@ skipping 50 matching lines @@
     return false;
   channel_main_->SetNeedsCommitOnImpl();
   return true;
 }
 
 bool ProxyMain::IsMainThread() const {
   return task_runner_provider_->IsMainThread();
 }
 
 }  // namespace cc