Implement lifetime observer on RenderWidgetHostViewBase.

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 5eb767921d4c4ee9746ecf1652b30c1393ceba05..d5d37cd4861fe7848ad262a276a59d69eaaa4332 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -563,13 +563,6 @@ RenderWidgetHostViewMac::~RenderWidgetHostViewMac() {
 
   UnlockMouse();
 
-  if (render_widget_host_ && render_widget_host_->delegate() &&
-      render_widget_host_->delegate()->GetInputEventRouter()) {
-    render_widget_host_->delegate()
-        ->GetInputEventRouter()
-        ->RemoveSurfaceIdNamespaceOwner(GetSurfaceIdNamespace());
-  }
-
   // Ensure that the browser compositor is destroyed in a safe order.
   ShutdownBrowserCompositor();
 
@@ -1060,6 +1053,9 @@ void RenderWidgetHostViewMac::RenderProcessGone(base::TerminationStatus status,
 }
 
 void RenderWidgetHostViewMac::Destroy() {
+  // SurfaceIdNamespaces registered with RenderWidgetHostInputEventRouter
+  // have already been cleared when RenderWidgetHostViewBase notified its
+  // observers of our impending destruction.
   [[NSNotificationCenter defaultCenter]
       removeObserver:cocoa_view_
                 name:NSWindowWillCloseNotification
@@ -1082,19 +1078,14 @@ void RenderWidgetHostViewMac::Destroy() {
   // object needs to survive until the stack unwinds.
   pepper_fullscreen_window_.autorelease();
 
-  // Clear SurfaceID namespace ownership before we shutdown the
-  // compositor.
-  if (render_widget_host_ && render_widget_host_->delegate() &&
-      render_widget_host_->delegate()->GetInputEventRouter()) {
-    render_widget_host_->delegate()
-        ->GetInputEventRouter()
-        ->RemoveSurfaceIdNamespaceOwner(GetSurfaceIdNamespace());
-  }
-
   // Delete the delegated frame state, which will reach back into
   // render_widget_host_.
   ShutdownBrowserCompositor();
 
+  // Make sure none of our observers send events for us to process after
+  // we release render_widget_host_.
+  NotifyObserversAboutShutdown();
+
   // We get this call just before |render_widget_host_| deletes
   // itself.  But we are owned by |cocoa_view_|, which may be retained
   // by some other code.  Examples are WebContentsViewMac's