(not for review yet)

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 220083f77f30b11cc53a38d723df0856f2da10b1..a88822896bfa2d61d890a47ee68fde90b4f37774 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -61,7 +61,7 @@ RendererCapabilities::RendererCapabilities()
 RendererCapabilities::~RendererCapabilities() {}
 
 UIResourceRequest::UIResourceRequest()
-    : type(UIResourceInvalidRequest), id(0), bitmap(NULL) {}
+    : type(UIResourceInvalidRequest), id(0), bitmap(NULL), ack(0) {}
 
 UIResourceRequest::~UIResourceRequest() {}
 
@@ -370,6 +370,13 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
       sync_tree->ProcessUIResourceRequestQueue();
   }
 
+  // If all UI resource evictions will not be acknowledged by this commit, then
+  // another commit is required.
+  if (ui_resource_eviction_count_last_acked_ !=
+      host_impl->ui_resource_eviction_count()) {
+    host_impl->SetNeedsCommit();
+  }
+
   DCHECK(!sync_tree->ViewportSizeInvalid());
 
   if (new_impl_tree_has_no_evicted_resources) {
@@ -1165,4 +1172,18 @@ void LayerTreeHost::RecreateUIResources(bool resource_lost) {
   }
 }
 
+void LayerTreeHost::SetUIResourceEvictionCountToAck(uint64 ui_resource_eviction_count) {
+  if (ui_resource_eviction_count_last_acked_ == ui_resource_eviction_count)
+    return;
+
+  bool resource_lost = false;
+  RecreateUIResources(resource_lost);
+
+  UIResourceRequest request;
+  request.type = UIResourceRequest::UIResourceEvictionAck;
+  request.ack = ui_resource_eviction_count;
+  ui_resource_request_queue_.push_back(request);
+  ui_resource_eviction_count_last_acked_ = ui_resource_eviction_count;
+}
+
 }  // namespace cc