Reland Fade out overlay scrollbar after page load

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index bf60a074e87f600b6c33f21f251f9e3be1c06bb7..3ce4e5570359a2aeabb1127f101936b6d19d80f8 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -2919,7 +2919,6 @@ class LayerTreeHostImplTestScrollbarAnimation : public LayerTreeHostImplTest {
     LayerImpl* root = host_impl_->active_tree()->InnerViewportContainerLayer();
     scrollbar->SetScrollElementId(scroll->element_id());
     root->test_properties()->AddChild(std::move(scrollbar));
-    scroll->set_needs_show_scrollbars(true);
     host_impl_->active_tree()->BuildPropertyTreesForTesting();
     host_impl_->active_tree()->DidBecomeActive();
     host_impl_->active_tree()->HandleScrollbarShowRequestsFromMain();
@@ -2943,7 +2942,8 @@ class LayerTreeHostImplTestScrollbarAnimation : public LayerTreeHostImplTest {
 
     base::TimeTicks fake_now = base::TimeTicks::Now();
 
-    if (expecting_animations) {
+    // Android Overlay Scrollbar does not have a initial show and fade out.
+    if (animator == LayerTreeSettings::AURA_OVERLAY) {
       // A task will be posted to fade the initial scrollbar.
       EXPECT_FALSE(did_request_next_frame_);
       EXPECT_FALSE(did_request_redraw_);
@@ -3223,7 +3223,6 @@ TEST_F(LayerTreeHostImplTest, ScrollbarVisibilityChangeCausesRedrawAndCommit) {
   scrollbar->SetPosition(gfx::PointF(90, 0));
   container->test_properties()->AddChild(std::move(scrollbar));
   host_impl_->pending_tree()->PushPageScaleFromMainThread(1.f, 1.f, 1.f);
-  scroll->set_needs_show_scrollbars(true);
   host_impl_->pending_tree()->BuildPropertyTreesForTesting();
   host_impl_->ActivateSyncTree();