Revert of cc: Split animating and drawing into separate actions

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 554b28f0ac5fd944884e5d6426237a87791fd176..36c71cee823e9594244303d25a7fad1048859003 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -470,9 +470,13 @@
                                   duration.InSecondsF());
   }
 
-  SetNeedsAnimate();
+  SetNeedsRedraw();
   client_->SetNeedsCommitOnImplThread();
   client_->RenewTreePriority();
+}
+
+void LayerTreeHostImpl::ScheduleAnimation() {
+  SetNeedsRedraw();
 }
 
 bool LayerTreeHostImpl::HaveTouchEventHandlersAt(
@@ -1714,11 +1718,6 @@
   renderer_->SetVisible(visible);
 }
 
-void LayerTreeHostImpl::SetNeedsAnimate() {
-  NotifySwapPromiseMonitorsOfSetNeedsRedraw();
-  client_->SetNeedsAnimateOnImplThread();
-}
-
 void LayerTreeHostImpl::SetNeedsRedraw() {
   NotifySwapPromiseMonitorsOfSetNeedsRedraw();
   client_->SetNeedsRedrawOnImplThread();
@@ -2714,8 +2713,6 @@
     page_scale_animation_.reset();
     client_->SetNeedsCommitOnImplThread();
     client_->RenewTreePriority();
-  } else {
-    SetNeedsAnimate();
   }
 }
 
@@ -2725,12 +2722,14 @@
   gfx::Vector2dF scroll = top_controls_manager_->Animate(time);
   if (active_tree_->TotalScrollOffset().y() == 0.f)
     return;
-  if (!scroll.IsZero()) {
+  if (scroll.IsZero()) {
+    // This may happen on the first animation step. Force redraw otherwise
+    // the animation would stop because of no new frames.
+    SetNeedsRedraw();
+  } else {
     ScrollViewportBy(gfx::ScaleVector2d(
         scroll, 1.f / active_tree_->total_page_scale_factor()));
-    SetNeedsRedraw();
-  }
-  SetNeedsAnimate();
+  }
 }
 
 void LayerTreeHostImpl::AnimateLayers(base::TimeTicks monotonic_time) {
@@ -2752,7 +2751,7 @@
        ++iter)
     (*iter).second->Animate(monotonic_time_for_cc_animations);
 
-  SetNeedsAnimate();
+  SetNeedsRedraw();
 }
 
 void LayerTreeHostImpl::UpdateAnimationState(bool start_ready_animations) {
@@ -2774,8 +2773,6 @@
   if (!events->empty()) {
     client_->PostAnimationEventsToMainThreadOnImplThread(events.Pass());
   }
-
-  SetNeedsAnimate();
 }
 
 base::TimeDelta LayerTreeHostImpl::LowFrequencyAnimationInterval() const {
@@ -2849,10 +2846,9 @@
       layer->scrollbar_animation_controller();
   if (scrollbar_controller && scrollbar_controller->Animate(time)) {
     TRACE_EVENT_INSTANT0(
-        "cc",
-        "LayerTreeHostImpl::SetNeedsAnimate due to AnimateScrollbars",
+        "cc", "LayerTreeHostImpl::SetNeedsRedraw due to AnimateScrollbars",
         TRACE_EVENT_SCOPE_THREAD);
-    SetNeedsAnimate();
+    SetNeedsRedraw();
   }
 
   for (size_t i = 0; i < layer->children().size(); ++i)
@@ -2873,11 +2869,10 @@
       layer->scrollbar_animation_controller();
   if (scrollbar_controller && scrollbar_controller->IsAnimating()) {
     base::TimeDelta delay = scrollbar_controller->DelayBeforeStart(time);
-    if (delay > base::TimeDelta()) {
+    if (delay > base::TimeDelta())
       client_->RequestScrollbarAnimationOnImplThread(delay);
-    } else if (scrollbar_controller->Animate(time)) {
-      SetNeedsAnimate();
-    }
+    else if (scrollbar_controller->Animate(time))
+      SetNeedsRedraw();
   }
 
   for (size_t i = 0; i < layer->children().size(); ++i)