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 a73a09ff790015c68ed33b744e1bbc1f3c9dd1a0..cffcca94e75ef6440e88f6adad85d18b8bd97f03 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();
 
@@ -1056,6 +1049,9 @@ void RenderWidgetHostViewMac::RenderProcessGone(base::TerminationStatus status,
 }
 
 void RenderWidgetHostViewMac::Destroy() {
+  // SurfaceIdNames registered with RenderWidgetHostInputEventRouter

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

nit: s/SurfaceIdNames/SurfaceIdNamespaces

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

Done.

+  // have already been cleared when RenderWidgetHostViewBase notified its
+  // observers of our impending destruction.
   [[NSNotificationCenter defaultCenter]
       removeObserver:cocoa_view_
                 name:NSWindowWillCloseNotification
@@ -1078,19 +1074,14 @@ 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