Mus+Ash: propagate Surface ID to parents

services/ui/public/interfaces/window_tree.mojom

Index: services/ui/public/interfaces/window_tree.mojom
diff --git a/services/ui/public/interfaces/window_tree.mojom b/services/ui/public/interfaces/window_tree.mojom
index c7f68eda14f6938d4804c58036ace972879bbf10..b3b8e082acf8dc4f371add3e74807cb5923349ea 100644
--- a/services/ui/public/interfaces/window_tree.mojom
+++ b/services/ui/public/interfaces/window_tree.mojom
@@ -5,6 +5,7 @@
 module ui.mojom;
 
 import "cc/ipc/surface_id.mojom";
+import "cc/ipc/surface_sequence.mojom";
 import "services/ui/public/interfaces/cursor.mojom";
 import "services/ui/public/interfaces/event_matcher.mojom";
 import "services/ui/public/interfaces/mus_constants.mojom";
@@ -142,6 +143,9 @@ interface WindowTree {
                 Surface& surface,
                 SurfaceClient client);
 
+  // Returns surface reference back to window server for reclamation.
+  ReturnSurfaceReference(uint32 window_id, cc.mojom.SurfaceSequence sequence);

[sky, 2016/10/14 20:55:46]

Can this name be more explicit, maybe something like OnWindowSurfaceDetached or
something, or OnWindowSurfaceNoLongerUsed? Or maye DestroyWindowSurface?

[Fady Samuel, 2016/10/14 21:32:48]

None of these are good names though because there may be multiple references to
a single surface ID (for thumbnailing or something). This returns just one
reference.

+
   // Reparents a window.
   // This fails for any of the following reasons:
   // . |parent| or |child| does not identify a valid window.
@@ -421,6 +425,15 @@ interface WindowTreeClient {
 
   OnWindowPredefinedCursorChanged(uint32 window_id, Cursor cursor_id);
 
+  // Invoked when a client window submits a new surface ID.

[sky, 2016/10/14 20:55:46]

Please better indicate what the client is expected to do here.

[Fady Samuel, 2016/10/14 21:32:48]

Done.

+  // TODO(fsamuel): Surface IDs should be passed to parents directly instead of
+  // going through the window server. http://crbug.com/655231
+  OnWindowSurfaceCreated(uint32 window_id,
+                         cc.mojom.SurfaceId surface_id,
+                         cc.mojom.SurfaceSequence surface_sequence,
+                         gfx.mojom.Size frame_size,
+                         float device_scale_factor);
+                         
   // Called when the mouse cursor enters a window on this connection for the
   // first time, providing a list of available mime types. We want to send this
   // set of data only one time, so this isn't part of OnDragEnter(), which