Remove scroll_clip_layer dependency from viewport layer tracking

cc/trees/layer_tree_host_unittest_picture.cc

Index: cc/trees/layer_tree_host_unittest_picture.cc
diff --git a/cc/trees/layer_tree_host_unittest_picture.cc b/cc/trees/layer_tree_host_unittest_picture.cc
index 55eabcb1eb7781104a60595a934e87689b40fd90..3d7c33b96e4539a749e55e5ae6c7c1e370514a59 100644
--- a/cc/trees/layer_tree_host_unittest_picture.cc
+++ b/cc/trees/layer_tree_host_unittest_picture.cc
@@ -423,8 +423,8 @@ class LayerTreeHostPictureTestRSLLMembershipWithScale
     picture_->SetBounds(gfx::Size(100, 100));
     pinch_->AddChild(picture_);
 
-    layer_tree_host()->RegisterViewportLayers(NULL, page_scale_layer, pinch_,
-                                              nullptr);
+    layer_tree_host()->RegisterViewportLayers(NULL, page_scale_layer, root_clip,
+                                              nullptr, pinch_, nullptr);
     layer_tree_host()->SetPageScaleFactorAndLimits(1.f, 1.f, 4.f);
     layer_tree_host()->SetRootLayer(root_clip);
     LayerTreeHostPictureTest::SetupTree();