Remove uses of external begin frame sources

cc/trees/proxy_impl.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_impl.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/auto_reset.h"
@@ skipping 59 matching lines @@
   const LayerTreeSettings& settings = layer_tree_host->GetSettings();
 
   SchedulerSettings scheduler_settings(settings.ToSchedulerSettings());
 
   std::unique_ptr<CompositorTimingHistory> compositor_timing_history(
       new CompositorTimingHistory(
           scheduler_settings.using_synchronous_renderer_compositor,
           CompositorTimingHistory::RENDERER_UMA,
           rendering_stats_instrumentation_));
 
-  // BFS must either be external or come from the output surface.  If
-  // external, it must be provided.  If from the output surface, it must
-  // not be provided.
-  // TODO(enne): Make all BFS come from the output surface.
-  DCHECK(settings.use_external_begin_frame_source ^
-         settings.use_output_surface_begin_frame_source);
-  DCHECK(!settings.use_external_begin_frame_source ||
-         external_begin_frame_source_);
-  DCHECK(!settings.use_output_surface_begin_frame_source ||
-         !external_begin_frame_source_);
+  // TODO(enne): remove these settings.
+  DCHECK(!settings.use_external_begin_frame_source);
+  DCHECK(settings.use_output_surface_begin_frame_source);
   scheduler_ = Scheduler::Create(this, scheduler_settings, layer_tree_host_id_,
                                  task_runner_provider_->ImplThreadTaskRunner(),
                                  external_begin_frame_source_.get(),
                                  std::move(compositor_timing_history));
 
   DCHECK_EQ(scheduler_->visible(), layer_tree_host_impl_->visible());
 }
 
 ProxyImpl::BlockedMainCommitOnly::BlockedMainCommitOnly()
     : layer_tree_host(nullptr) {}
@@ skipping 529 matching lines @@
 bool ProxyImpl::IsMainThreadBlocked() const {
   return task_runner_provider_->IsMainThreadBlocked();
 }
 
 ProxyImpl::BlockedMainCommitOnly& ProxyImpl::blocked_main_commit() {
   DCHECK(IsMainThreadBlocked() && commit_completion_event_);
   return main_thread_blocked_commit_vars_unsafe_;
 }
 
 }  // namespace cc