Remove invalid check

extensions/browser/app_window/app_window.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/browser/app_window/app_window.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 466 matching lines @@
     Show(delayed_show_type_);
   }
 }
 
 void AppWindow::SetOnFirstCommitCallback(const base::Closure& callback) {
   DCHECK(on_first_commit_callback_.is_null());
   on_first_commit_callback_ = callback;
 }
 
 void AppWindow::OnReadyToCommitFirstNavigation() {
-  CHECK(content::IsBrowserSideNavigationEnabled());
+  if (!content::IsBrowserSideNavigationEnabled())
+    return;
+
+  // PlzNavigate: execute renderer-side setup now that there is a renderer
+  // process assigned to the navigation. With renderer-side navigation, this
+  // would happen before the navigation starts, but PlzNavigate must wait until
+  // this point in time in the navigation.
+
   WindowEventsReady();
   if (on_first_commit_callback_.is_null())
     return;
   // It is important that the callback executes after the calls to
   // WebContentsObserver::ReadyToCommitNavigation have been processed. The
   // CommitNavigation IPC that will properly set up the renderer will only be
   // sent after these, and it must be sent before the callback gets to run,
   // hence the use of PostTask.
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::ResetAndReturn(&on_first_commit_callback_));
@@ skipping 657 matching lines @@
         region.bounds.x(),
         region.bounds.y(),
         region.bounds.right(),
         region.bounds.bottom(),
         region.draggable ? SkRegion::kUnion_Op : SkRegion::kDifference_Op);
   }
   return sk_region;
 }
 
 }  // namespace extensions