Replace layer id with Element id for tracking scrollbar animation controllers

cc/test/fake_painted_scrollbar_layer.cc

Index: cc/test/fake_painted_scrollbar_layer.cc
diff --git a/cc/test/fake_painted_scrollbar_layer.cc b/cc/test/fake_painted_scrollbar_layer.cc
index e479e4a263f0dfdbea7787f8f275e95154483d29..aca20a9a523896d061333617425f2021c1b59c7c 100644
--- a/cc/test/fake_painted_scrollbar_layer.cc
+++ b/cc/test/fake_painted_scrollbar_layer.cc
@@ -13,9 +13,10 @@ namespace cc {
 scoped_refptr<FakePaintedScrollbarLayer> FakePaintedScrollbarLayer::Create(
     bool paint_during_update,
     bool has_thumb,
-    int scrolling_layer_id) {
+    int scrolling_layer_id,
+    ElementId scrolling_element_id) {
   return Create(paint_during_update, has_thumb, HORIZONTAL, false, false,
-                scrolling_layer_id);
+                scrolling_layer_id, scrolling_element_id);
 }
 
 scoped_refptr<FakePaintedScrollbarLayer> FakePaintedScrollbarLayer::Create(
@@ -24,19 +25,22 @@ scoped_refptr<FakePaintedScrollbarLayer> FakePaintedScrollbarLayer::Create(
     ScrollbarOrientation orientation,
     bool is_left_side_vertical_scrollbar,
     bool is_overlay,
-    int scrolling_layer_id) {
+    int scrolling_layer_id,
+    ElementId scrolling_element_id) {
   FakeScrollbar* fake_scrollbar =
       new FakeScrollbar(paint_during_update, has_thumb, orientation,
                         is_left_side_vertical_scrollbar, is_overlay);
-  return make_scoped_refptr(
-      new FakePaintedScrollbarLayer(fake_scrollbar, scrolling_layer_id));
+  return make_scoped_refptr(new FakePaintedScrollbarLayer(
+      fake_scrollbar, scrolling_layer_id, scrolling_element_id));
 }
 
 FakePaintedScrollbarLayer::FakePaintedScrollbarLayer(
     FakeScrollbar* fake_scrollbar,
-    int scrolling_layer_id)
+    int scrolling_layer_id,
+    ElementId scrolling_element_id)
     : PaintedScrollbarLayer(std::unique_ptr<Scrollbar>(fake_scrollbar),
-                            scrolling_layer_id),
+                            scrolling_layer_id,
+                            scrolling_element_id),
       update_count_(0),
       push_properties_count_(0),
       fake_scrollbar_(fake_scrollbar) {