Remove external begin frame source parameter and settings

cc/layers/layer_position_constraint_unittest.cc

Index: cc/layers/layer_position_constraint_unittest.cc
diff --git a/cc/layers/layer_position_constraint_unittest.cc b/cc/layers/layer_position_constraint_unittest.cc
index 23130305e3d10a5d8ae490df1e634c9570cc4f2c..842d20b6549eacf08aaa780d02331dffa86ca665 100644
--- a/cc/layers/layer_position_constraint_unittest.cc
+++ b/cc/layers/layer_position_constraint_unittest.cc
@@ -73,7 +73,7 @@ class LayerPositionConstraintTest : public testing::Test {
         great_grand_child_impl_(nullptr) {
     layer_tree_host_->InitializeForTesting(
         TaskRunnerProvider::Create(nullptr, nullptr),
-        std::unique_ptr<Proxy>(new FakeProxy), nullptr);
+        std::unique_ptr<Proxy>(new FakeProxy));
     CreateTreeForTest();
     fixed_to_top_left_.set_is_fixed_position(true);
     fixed_to_bottom_right_.set_is_fixed_position(true);