cc: Remove BeginFrameSource::Create methods

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index fa193bf3e0a63f7b0b0c23d1279dfaa77b61e21e..5fcb39b117085fcb341899d682d6556979616c98 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -74,14 +74,14 @@ void SingleThreadProxy::Start(
     BeginFrameSource* frame_source = external_begin_frame_source_.get();
     if (!scheduler_settings.throttle_frame_production) {
       // Unthrottled source takes precedence over external sources.
-      unthrottled_begin_frame_source_ = BackToBackBeginFrameSource::Create(
-          task_runner_provider_->MainThreadTaskRunner());
+      unthrottled_begin_frame_source_.reset(new BackToBackBeginFrameSource(
+          task_runner_provider_->MainThreadTaskRunner()));
       frame_source = unthrottled_begin_frame_source_.get();
     }
     if (!frame_source) {
-      synthetic_begin_frame_source_ = SyntheticBeginFrameSource::Create(
+      synthetic_begin_frame_source_.reset(new SyntheticBeginFrameSource(
           task_runner_provider_->MainThreadTaskRunner(),
-          BeginFrameArgs::DefaultInterval());
+          BeginFrameArgs::DefaultInterval()));
       frame_source = synthetic_begin_frame_source_.get();
     }