Implement temporary reference assignment with DisplayCompositor.

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index 6ca22491bff3e8bf6f985344f2a000304df293ae..bf6a7f5369d7806f2c8138bd18797aad9c9f4d0f 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -606,6 +606,30 @@ bool WindowServer::IsUserInHighContrastMode(const UserId& user) const {
   return (iter == high_contrast_mode_.end()) ? false : iter->second;
 }
 
+ServerWindow* WindowServer::FindCompositorFrameSinkParent(

[Fady Samuel, 2017/02/24 18:07:38]

nit: TODO that we should plumb a bool to ServerWindow to indicate that they will
create CompositorFrames / CompositorFrameSinks.

[kylechar, 2017/02/28 18:07:17]

Done.

+    ServerWindow* window) {
+  DCHECK(window->parent());
+
+  WindowTree* window_tree = GetTreeWithId(window->parent()->id().client_id);
+  if (window_tree) {
+    // If the parent of |window| is part of a WindowTree, the WindowTree root
+    // that contains |window| should be backed by a CompositorFrameSink.
+    for (const ServerWindow* root : window_tree->roots()) {
+      if (root->Contains(window))
+        // TODO(kylechar): There must be a better way to do this.
+        return const_cast<ServerWindow*>(root);
+    }
+  }
+
+  // The parent of |window| might be a display root which isn't part of a
+  // WindowTree. Display roots will always be backed by a CompositorFrameSink.
+  Display* display = display_manager_->GetDisplayContaining(window);
+  if (display && display->root_window() == window->parent())
+    return display->root_window();
+
+  return nullptr;
+}
+
 ServerWindow* WindowServer::GetRootWindow(const ServerWindow* window) {
   Display* display = display_manager_->GetDisplayContaining(window);
   return display ? display->root_window() : nullptr;
@@ -761,8 +785,6 @@ void WindowServer::OnTransientWindowRemoved(ServerWindow* window,
 }
 
 void WindowServer::OnGpuServiceInitialized() {
-  // TODO(kylechar): When gpu channel is removed, this can instead happen
-  // earlier, after GpuHost::OnInitialized().
   delegate_->StartDisplayInit();
 }
 
@@ -771,8 +793,10 @@ void WindowServer::OnSurfaceCreated(const cc::SurfaceInfo& surface_info) {
       WindowIdFromTransportId(surface_info.id().frame_sink_id().client_id()));
   ServerWindow* window = GetWindow(window_id);
   // If the window doesn't have a parent then we have nothing to propagate.
-  if (!window)
+  if (!window) {
+    display_compositor_->DropTemporaryReference(surface_info.id());
     return;
+  }
 
   // FrameGenerator will add an appropriate reference for the new surface.
   DCHECK(display_manager_->GetDisplayContaining(window));
@@ -787,12 +811,24 @@ void WindowServer::OnSurfaceCreated(const cc::SurfaceInfo& surface_info) {
   if (!window_paint_callback_.is_null())
     window_paint_callback_.Run(window);
 
-  if (!window->parent())
+  if (!window->parent()) {
+    // If |window| is a display root then a surface reference has already been
+    // added by the DisplayCompositor.
+    display_compositor_->DropTemporaryReference(surface_info.id());
     return;
+  }
 
   WindowTree* window_tree = GetTreeWithId(window->parent()->id().client_id);
   if (window_tree)
     window_tree->ProcessWindowSurfaceChanged(window, surface_info);
+
+  ServerWindow* parent = FindCompositorFrameSinkParent(window);

[Fady Samuel, 2017/02/24 18:07:38]

nit: compositing_parent

[kylechar, 2017/02/28 18:07:16]

Done.

+  if (parent) {
+    auto* frame_sink_manager = parent->GetOrCreateCompositorFrameSinkManager();
+    frame_sink_manager->ClaimTemporaryReference(surface_info.id());

[Fady Samuel, 2017/02/24 18:07:38]

Add a comment here about what this is doing.

[kylechar, 2017/02/28 18:07:15]

Done.

+  } else {
+    display_compositor_->DropTemporaryReference(surface_info.id());
+  }
 }
 
 void WindowServer::OnActiveUserIdChanged(const UserId& previously_active_id,