Standardize usage of virtual/override/final in content/

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index bc33726b6e50cd3e7ea0db4076c7c668f682e716..8ebce62667a619dbf346a0c783c974dc1d1da234 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -450,7 +450,7 @@ class ContentMainRunnerImpl : public ContentMainRunner {
 #endif
   }
 
-  virtual ~ContentMainRunnerImpl() {
+  ~ContentMainRunnerImpl() override {
     if (is_initialized_ && !is_shutdown_)
       Shutdown();
   }
@@ -480,7 +480,7 @@ class ContentMainRunnerImpl : public ContentMainRunner {
   }
 #endif
 
-  virtual int Initialize(const ContentMainParams& params) override {
+  int Initialize(const ContentMainParams& params) override {
     ui_task_ = params.ui_task;
 
 #if defined(OS_WIN)
@@ -749,7 +749,7 @@ class ContentMainRunnerImpl : public ContentMainRunner {
     return -1;
   }
 
-  virtual int Run() override {
+  int Run() override {
     DCHECK(is_initialized_);
     DCHECK(!is_shutdown_);
     const base::CommandLine& command_line =
@@ -772,7 +772,7 @@ class ContentMainRunnerImpl : public ContentMainRunner {
 #endif
   }
 
-  virtual void Shutdown() override {
+  void Shutdown() override {
     DCHECK(is_initialized_);
     DCHECK(!is_shutdown_);