Remove external begin frame source parameter and settings

cc/trees/tree_synchronizer_unittest.cc

Index: cc/trees/tree_synchronizer_unittest.cc
diff --git a/cc/trees/tree_synchronizer_unittest.cc b/cc/trees/tree_synchronizer_unittest.cc
index 6ad3e99ead4cde98918cacff04a6a005e86f69a0..bc386780853a7ecfc9749363a5536588aefb9633 100644
--- a/cc/trees/tree_synchronizer_unittest.cc
+++ b/cc/trees/tree_synchronizer_unittest.cc
@@ -564,7 +564,7 @@ TEST_F(TreeSynchronizerTest, SynchronizeCurrentlyScrollingNode) {
 
 TEST_F(TreeSynchronizerTest, SynchronizeScrollTreeScrollOffsetMap) {
   host_->InitializeSingleThreaded(&single_thread_client_,
-                                  base::ThreadTaskRunnerHandle::Get(), nullptr);
+                                  base::ThreadTaskRunnerHandle::Get());
   LayerTreeSettings settings;
   FakeLayerTreeHostImplClient client;
   FakeImplTaskRunnerProvider task_runner_provider;
@@ -660,7 +660,7 @@ TEST_F(TreeSynchronizerTest, SynchronizeScrollTreeScrollOffsetMap) {
 
 TEST_F(TreeSynchronizerTest, RefreshPropertyTreesCachedData) {
   host_->InitializeSingleThreaded(&single_thread_client_,
-                                  base::ThreadTaskRunnerHandle::Get(), nullptr);
+                                  base::ThreadTaskRunnerHandle::Get());
   LayerTreeSettings settings;
   FakeLayerTreeHostImplClient client;
   FakeImplTaskRunnerProvider task_runner_provider;