Standardize usage of virtual/override/final in chrome/browser/

BUG=417463
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Review URL: https://codereview.chromium.org/648653003

Cr-Commit-Position: refs/heads/master@{#300440}
diff --git a/chrome/browser/pepper_flash_settings_manager.cc b/chrome/browser/pepper_flash_settings_manager.cc
index 74caec5..7dad619 100644
--- a/chrome/browser/pepper_flash_settings_manager.cc
+++ b/chrome/browser/pepper_flash_settings_manager.cc
@@ -64,8 +64,8 @@
                      uint64 max_age);
 
   // IPC::Listener implementation.
-  virtual bool OnMessageReceived(const IPC::Message& message) override;
-  virtual void OnChannelError() override;
+  bool OnMessageReceived(const IPC::Message& message) override;
+  void OnChannelError() override;
 
  private:
   friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>;
@@ -119,7 +119,7 @@
     uint64 max_age;
   };
 
-  virtual ~Core();
+  ~Core() override;
 
   void ConnectToChannel(bool success, const IPC::ChannelHandle& handle);