(not for review yet)

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 52a539b94f461e920800d4421991b37e3283012a..18c77dbcaf0f076301a2220337f3acaf1fc30a86 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -33,6 +33,7 @@ LayerTreeImpl::LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl)
       min_page_scale_factor_(0),
       max_page_scale_factor_(0),
       scrolling_layer_id_from_previous_tree_(0),
+      ui_resource_eviction_count_acked_(0),
       contents_textures_purged_(false),
       viewport_size_invalid_(false),
       needs_update_draw_properties_(true),
@@ -126,6 +127,9 @@ void LayerTreeImpl::PushPropertiesTo(LayerTreeImpl* target_tree) {
   else
     target_tree->ResetContentsTexturesPurged();
 
+  target_tree->SetUIResourceEvictionCountAcked(
+      ui_resource_eviction_count_acked());
+
   if (ViewportSizeInvalid())
     target_tree->SetViewportSizeInvalid();
   else
@@ -382,6 +386,15 @@ void LayerTreeImpl::DidBecomeActive() {
   FindRootScrollLayer();
 }
 
+void LayerTreeImpl::SetUIResourceEvictionCountAcked(
+    uint64 ui_resource_eviction_count_acked) {
+  if (ui_resource_eviction_count_acked == ui_resource_eviction_count_acked_)
+    return;
+
+  ui_resource_eviction_count_acked_ = ui_resource_eviction_count_acked;
+  layer_tree_host_impl_->OnCanDrawStateChangedForTree();
+}
+
 bool LayerTreeImpl::ContentsTexturesPurged() const {
   return contents_textures_purged_;
 }
@@ -619,6 +632,9 @@ void LayerTreeImpl::ProcessUIResourceRequestQueue() {
       case UIResourceRequest::UIResourceDelete:
         layer_tree_host_impl_->DeleteUIResource(req.id);
         break;
+      case UIResourceRequest::UIResourceEvictionAck:
+        SetUIResourceEvictionCountAcked(req.ack);
+        break;
       case UIResourceRequest::UIResourceInvalidRequest:
         NOTREACHED();
         break;