Generalize layer mirroring for phantom windows

components/exo/surface.cc

Index: components/exo/surface.cc
diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index ab4cf7b60c9256fe7fec22ef40e6c162558a8ad8..e027bfa40f80b19899638b4b06669c8305311215 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -484,13 +484,16 @@ void Surface::CommitSurfaceHierarchy() {
 
   if (old_surface_id != surface_id_) {
     float contents_surface_to_layer_scale = 1.0;
+    // The bounds must be updated before switching to the new surface, because
+    // the layer may be mirrored, in which case a surface change causes the
+    // mirror layer to update its surface using the latest bounds.
+    window_->layer()->SetBounds(
+        gfx::Rect(window_->layer()->bounds().origin(), content_size_));
     window_->layer()->SetShowSurface(
         surface_id_,
         base::Bind(&SatisfyCallback, base::Unretained(surface_manager_)),
         base::Bind(&RequireCallback, base::Unretained(surface_manager_)),
         content_size_, contents_surface_to_layer_scale, content_size_);
-    window_->layer()->SetBounds(
-        gfx::Rect(window_->layer()->bounds().origin(), content_size_));
     window_->layer()->SetFillsBoundsOpaquely(
         state_.blend_mode == SkXfermode::kSrc_Mode ||
         state_.opaque_region.contains(
@@ -610,13 +613,13 @@ std::unique_ptr<base::trace_event::TracedValue> Surface::AsTracedValue() const {
 // ui::LayerOwnerDelegate overrides:
 
 void Surface::OnLayerRecreated(ui::Layer* old_layer, ui::Layer* new_layer) {
-  if (!current_buffer_.buffer())
-    return;
-
-  // TODO(reveman): Give the client a chance to provide new contents.
   SetSurfaceLayerContents(new_layer);
 }
 
+void Surface::OnLayerMirrored(ui::Layer* mirror) {
+  SetSurfaceLayerContents(mirror);
+}
+
 void Surface::WillDraw(const cc::SurfaceId& id) {
   while (!active_frame_callbacks_.empty()) {
     active_frame_callbacks_.front().Run(base::TimeTicks::Now());
@@ -692,12 +695,13 @@ void Surface::SetSurfaceHierarchyNeedsCommitToNewSurfaces() {
 }
 
 void Surface::SetSurfaceLayerContents(ui::Layer* layer) {
-  if (surface_id_.is_null())
+  if (!current_buffer_.buffer() || surface_id_.is_null())
     return;
 
   gfx::Size layer_size = layer->bounds().size();
   float contents_surface_to_layer_scale = 1.0f;
 
+  // TODO(reveman): Give the client a chance to provide new contents.
   layer->SetShowSurface(
       surface_id_,
       base::Bind(&SatisfyCallback, base::Unretained(surface_manager_)),