Remove NOTIFICATION_RENDER_VIEW_HOST_CHANGED.

chrome/browser/ui/panels/panel.cc

Index: chrome/browser/ui/panels/panel.cc
diff --git a/chrome/browser/ui/panels/panel.cc b/chrome/browser/ui/panels/panel.cc
index 949c612a845b03667f95e7eda74920108d6feaf2..72c38f335bb97e1accc3c68d469a6a8f69c8ec38 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -437,9 +437,6 @@ void Panel::Observe(int type,
                     const content::NotificationSource& source,
                     const content::NotificationDetails& details) {
   switch (type) {
-    case content::NOTIFICATION_RENDER_VIEW_HOST_CHANGED:
-      ConfigureAutoResize(content::Source<content::WebContents>(source).ptr());
-      break;
     case chrome::NOTIFICATION_APP_TERMINATING:
       Close();
       break;
@@ -448,6 +445,11 @@ void Panel::Observe(int type,
   }
 }
 
+void Panel::RenderViewHostChanged(content::RenderViewHost* old_host,
+                                  content::RenderViewHost* new_host) {
+  ConfigureAutoResize(web_contents());
+}
+
 void Panel::OnExtensionUnloaded(
     content::BrowserContext* browser_context,
     const extensions::Extension* extension,
@@ -593,8 +595,7 @@ void Panel::SetAutoResizable(bool resizable) {
       EnableWebContentsAutoResize(web_contents);
   } else {
     if (web_contents) {
-      registrar_.Remove(this, content::NOTIFICATION_RENDER_VIEW_HOST_CHANGED,
-                        content::Source<content::WebContents>(web_contents));
+      content::WebContentsObserver::Observe(nullptr);
 
       // NULL might be returned if the tab has not been added.
       RenderViewHost* render_view_host = web_contents->GetRenderViewHost();
@@ -610,14 +611,7 @@ void Panel::EnableWebContentsAutoResize(content::WebContents* web_contents) {
 
   // We also need to know when the render view host changes in order
   // to turn on auto-resize notifications in the new render view host.
-  if (!registrar_.IsRegistered(
-          this, content::NOTIFICATION_RENDER_VIEW_HOST_CHANGED,
-          content::Source<content::WebContents>(web_contents))) {
-    registrar_.Add(
-        this,
-        content::NOTIFICATION_RENDER_VIEW_HOST_CHANGED,
-        content::Source<content::WebContents>(web_contents));
-  }
+  content::WebContentsObserver::Observe(web_contents);
 }
 
 void Panel::OnContentsAutoResized(const gfx::Size& new_content_size) {
@@ -803,7 +797,8 @@ Panel::Panel(Profile* profile,
              const std::string& app_name,
              const gfx::Size& min_size,
              const gfx::Size& max_size)
-    : app_name_(app_name),
+    : content::WebContentsObserver(),
+      app_name_(app_name),
       profile_(profile),
       collection_(NULL),
       initialized_(false),