Share animations from compositor to main thread.

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index aa34a8d3a715f9adaddfe1d26ed702515f60423a..f4b211a7d8e41967005323e7b4df0787b8ee2016 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -14,6 +14,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
+#include "cc/animation/animation_host.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/mutable_properties.h"
 #include "cc/base/math_util.h"
@@ -499,6 +500,26 @@ scoped_ptr<LayerImpl> LayerImpl::CreateLayerImpl(LayerTreeImpl* tree_impl) {
   return LayerImpl::Create(tree_impl, layer_id_, scroll_offset_);
 }
 
+void LayerImpl::set_main_thread_scrolling_reasons(
+    uint32_t main_thread_scrolling_reasons) {
+  if (main_thread_scrolling_reasons_ == main_thread_scrolling_reasons)
+    return;
+
+  if (main_thread_scrolling_reasons &
+          MainThreadScrollingReason::kHasNonLayerViewportConstrainedObjects &&
+      layer_tree_impl()) {
+    if (layer_tree_impl()->ScrollOffsetIsAnimatingOnImplOnly(this)) {
+      layer_tree_impl()->animation_host()->ScrollAnimationAbort(
+          true /* needs_completion */);
+    } else if (layer_animation_controller()) {
+      layer_animation_controller()->AbortAnimations(

[ajuma, 2016/02/26 23:56:54]

Shouldn't this be only if the animations are impl-only? That said, the old
animation code path is close to being deleted (see crbug.com/575041), so this
might not end up mattering by the time this lands.

[ymalik, 2016/02/29 16:31:09]

Yes, you're right. I am removing it though, since I don't have the takeover
pluming for the old path anyway.

+          TargetProperty::SCROLL_OFFSET, true /* needs_completion */);
+    }
+  }
+
+  main_thread_scrolling_reasons_ = main_thread_scrolling_reasons;
+}
+
 void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->SetTransformOrigin(transform_origin_);
   layer->SetBackgroundColor(background_color_);