Replace deprecated base::NonThreadSafe in chrome in favor of SequenceChecker.

chrome/browser/after_startup_task_utils.cc

Index: chrome/browser/after_startup_task_utils.cc
diff --git a/chrome/browser/after_startup_task_utils.cc b/chrome/browser/after_startup_task_utils.cc
index 1ba1bd5529627ea2f916b764962b28ac9c214bb0..5c032d1da9a4af0a93d625c8e2f12262886c99c5 100644
--- a/chrome/browser/after_startup_task_utils.cc
+++ b/chrome/browser/after_startup_task_utils.cc
@@ -13,6 +13,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/process/process_info.h"
 #include "base/rand_util.h"
+#include "base/sequence_checker.h"
 #include "base/synchronization/atomic_flag.h"
 #include "base/task_runner.h"
 #include "base/tracked_objects.h"
@@ -122,16 +123,19 @@ void SetBrowserStartupIsComplete() {
 
 // Observes the first visible page load and sets the startup complete
 // flag accordingly.
-class StartupObserver : public WebContentsObserver, public base::NonThreadSafe {
+class StartupObserver : public WebContentsObserver {
  public:
   StartupObserver() : weak_factory_(this) {}
-  ~StartupObserver() override { DCHECK(IsBrowserStartupComplete()); }
+  ~StartupObserver() override {
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+    DCHECK(IsBrowserStartupComplete());
+  }
 
   void Start();
 
  private:
   void OnStartupComplete() {
-    DCHECK(CalledOnValidThread());
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
     SetBrowserStartupIsComplete();
     delete this;
   }
@@ -156,6 +160,8 @@ class StartupObserver : public WebContentsObserver, public base::NonThreadSafe {
 
   void WebContentsDestroyed() override { OnStartupComplete(); }
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   base::WeakPtrFactory<StartupObserver> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(StartupObserver);