Restore original WebView SurfaceId after showing interstitial.

content/browser/frame_host/render_widget_host_view_child_frame.cc

Index: content/browser/frame_host/render_widget_host_view_child_frame.cc
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.cc b/content/browser/frame_host/render_widget_host_view_child_frame.cc
index 0492c269cf5f3bab35ef63095a9fd4cfc018da89..9344bd36013dd8daffc70e10f988ea47c17fb4c8 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.cc
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.cc
@@ -33,7 +33,6 @@ RenderWidgetHostViewChildFrame::RenderWidgetHostViewChildFrame(
     RenderWidgetHost* widget_host)
     : host_(RenderWidgetHostImpl::From(widget_host)),
       use_surfaces_(UseSurfacesEnabled()),
-      next_surface_sequence_(1u),
       last_output_surface_id_(0),
       current_surface_scale_factor_(1.f),
       ack_pending_count_(0),
@@ -300,14 +299,15 @@ void RenderWidgetHostViewChildFrame::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_);
     frame_connector_->SetChildFrameSurface(surface_id_, frame_size,
-                                           scale_factor, sequence);
+                                           scale_factor, surface_sequence_);
   }
 
   cc::SurfaceFactory::DrawCallback ack_callback =