Restore original WebView SurfaceId after showing interstitial.

content/browser/frame_host/render_widget_host_view_guest.cc

Index: content/browser/frame_host/render_widget_host_view_guest.cc
diff --git a/content/browser/frame_host/render_widget_host_view_guest.cc b/content/browser/frame_host/render_widget_host_view_guest.cc
index 656f2e80c73f2492052218469ed6aa6c2c21f532..c0f2c1be65838132c11429c9793c1bc384e11ff9 100644
--- a/content/browser/frame_host/render_widget_host_view_guest.cc
+++ b/content/browser/frame_host/render_widget_host_view_guest.cc
@@ -95,8 +95,14 @@ void RenderWidgetHostViewGuest::Show() {
   // The two sizes may fall out of sync if we switch RenderWidgetHostViews,
   // resize, and then switch page, as is the case with interstitial pages.
   // NOTE: |guest_| is NULL in unit tests.
-  if (guest_)
+  if (guest_) {
     SetSize(guest_->web_contents()->GetViewBounds().size());
+    if (!surface_id_.is_null()) {
+      guest_->SetChildFrameSurface(surface_id_, current_surface_size_,
+                                   current_surface_scale_factor_,
+                                   surface_sequence_);

[kenrb, 2015/11/25 21:44:02]

I wonder if it might be safer to destroy any existing Surface here. The
SurfaceManager gets rid of Surfaces that are not being used anymore, because all
of their dependencies have been satisfied. The purpose of passing the
SurfaceSequence to SetChildFrameSurface is actually because
OnSwapCompositorFrame creates a temporary dependency on the new Surface,
protecting it from the SurfaceManager's garbage collection. Then the embedding
renderer satisfies that dependency after it has created its own (see
BrowserPluginGuest::OnSatisfySequence and OnRequireSequence). When the Surface
gets replaced in the embedder with the interstitial's Surface, I would worry
that the original might get destroyed because it no longer has any destruction
dependencies and it becomes unreachable in the surface tree.

You might want to check with jbauman@ on this, in any case.

[wjmaclean, 2015/11/25 21:50:17]

Acknowledged.

+    }
+  }
   host_->WasShown(ui::LatencyInfo());
 }
 
@@ -255,14 +261,15 @@ void RenderWidgetHostViewGuest::OnSwapCompositorFrame(
     surface_id_ = id_allocator_->GenerateId();
     surface_factory_->Create(surface_id_);
 
-    cc::SurfaceSequence sequence = cc::SurfaceSequence(
-        id_allocator_->id_namespace(), next_surface_sequence_++);
+    surface_sequence_ = cc::SurfaceSequence(
+        id_allocator_->id_namespace(), surface_sequence_.sequence + 1);
     // The renderer process will satisfy this dependency when it creates a
     // SurfaceLayer.
     cc::SurfaceManager* manager = GetSurfaceManager();
-    manager->GetSurfaceForId(surface_id_)->AddDestructionDependency(sequence);
+    manager->GetSurfaceForId(surface_id_)
+        ->AddDestructionDependency(surface_sequence_);
     guest_->SetChildFrameSurface(surface_id_, frame_size, scale_factor,
-                                 sequence);
+                                 surface_sequence_);
   }
 
   cc::SurfaceFactory::DrawCallback ack_callback = base::Bind(