Implement lifetime observer on RenderWidgetHostViewBase.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index d78031f1fa4004f3483318d2fb8e844fe5484c60..3536d1b7b89f7d6cb72cdc161a1b94687ccd7699 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -2486,6 +2486,10 @@ void RenderWidgetHostViewAura::OnHostMoved(const aura::WindowTreeHost* host,
 // RenderWidgetHostViewAura, private:
 
 RenderWidgetHostViewAura::~RenderWidgetHostViewAura() {
+  // If the observers were already notified through the Destroy() pathway, then
+  // this next call just returns.

[kenrb, 2016/02/22 17:05:10]

Is this comment necessary? RWHVA::Destroy() doesn't seem to notify observers.

[wjmaclean, 2016/02/23 13:13:26]

Done.

Ooops, slightly stale comment, removed. Actually, we may be able to remove this
call to NotifyObserversAboutShutdown() altogether, since we don't destroy
anything like a host_ here, and the RWHVB destructor will call this function
shortly.

+  NotifyObserversAboutShutdown();
+
   // Ask the RWH to drop reference to us.
   if (!is_guest_view_hack_)
     host_->ViewDestroyed();
@@ -2493,10 +2497,6 @@ RenderWidgetHostViewAura::~RenderWidgetHostViewAura() {
   selection_controller_.reset();
   selection_controller_client_.reset();
 
-  if (host_->delegate() && host_->delegate()->GetInputEventRouter()) {
-    host_->delegate()->GetInputEventRouter()->RemoveSurfaceIdNamespaceOwner(
-        GetSurfaceIdNamespace());
-  }
   delegated_frame_host_.reset();
   window_observer_.reset();
   if (window_) {