Add a few missing overrides found by a new clang warning.

ui/base/dragdrop/os_exchange_data_provider_win.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_WIN_H_
 #define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_WIN_H_
 
 #include <objidl.h>
 #include <shlobj.h>
 #include <string>
@@ skipping 130 matching lines @@
 
   explicit OSExchangeDataProviderWin(IDataObject* source);
   OSExchangeDataProviderWin();
 
   virtual ~OSExchangeDataProviderWin();
 
   IDataObject* data_object() const { return data_.get(); }
   IDataObjectAsyncCapability* async_operation() const { return data_.get(); }
 
   // OSExchangeData::Provider methods.
-  virtual Provider* Clone() const;
-  virtual void MarkOriginatedFromRenderer();
-  virtual bool DidOriginateFromRenderer() const;
-  virtual void SetString(const base::string16& data);
-  virtual void SetURL(const GURL& url, const base::string16& title);
-  virtual void SetFilename(const base::FilePath& path);
-  virtual void SetFilenames(const std::vector<FileInfo>& filenames);
-  virtual void SetPickledData(const OSExchangeData::CustomFormat& format,
-                              const Pickle& data);
-  virtual void SetFileContents(const base::FilePath& filename,
-                               const std::string& file_contents);
-  virtual void SetHtml(const base::string16& html, const GURL& base_url);
+  Provider* Clone() const override;
+  void MarkOriginatedFromRenderer() override;
+  bool DidOriginateFromRenderer() const override;
+  void SetString(const base::string16& data) override;
+  void SetURL(const GURL& url, const base::string16& title) override;
+  void SetFilename(const base::FilePath& path) override;
+  void SetFilenames(const std::vector<FileInfo>& filenames) override;
+  void SetPickledData(const OSExchangeData::CustomFormat& format,
+                      const Pickle& data) override;
+  void SetFileContents(const base::FilePath& filename,
+                       const std::string& file_contents) override;
+  void SetHtml(const base::string16& html, const GURL& base_url) override;
 
-  virtual bool GetString(base::string16* data) const;
-  virtual bool GetURLAndTitle(OSExchangeData::FilenameToURLPolicy policy,
-                              GURL* url,
-                              base::string16* title) const;
-  virtual bool GetFilename(base::FilePath* path) const;
-  virtual bool GetFilenames(std::vector<FileInfo>* filenames) const;
-  virtual bool GetPickledData(const OSExchangeData::CustomFormat& format,
-                              Pickle* data) const;
-  virtual bool GetFileContents(base::FilePath* filename,
-                               std::string* file_contents) const;
-  virtual bool GetHtml(base::string16* html, GURL* base_url) const;
-  virtual bool HasString() const;
-  virtual bool HasURL(OSExchangeData::FilenameToURLPolicy policy) const;
-  virtual bool HasFile() const;
-  virtual bool HasFileContents() const;
-  virtual bool HasHtml() const;
-  virtual bool HasCustomFormat(
-      const OSExchangeData::CustomFormat& format) const;
-  virtual void SetDownloadFileInfo(
-      const OSExchangeData::DownloadFileInfo& download_info);
-  virtual void SetDragImage(const gfx::ImageSkia& image,
-                            const gfx::Vector2d& cursor_offset) override;
-  virtual const gfx::ImageSkia& GetDragImage() const override;
-  virtual const gfx::Vector2d& GetDragImageOffset() const override;
+  bool GetString(base::string16* data) const override;
+  bool GetURLAndTitle(OSExchangeData::FilenameToURLPolicy policy,
+                      GURL* url,
+                      base::string16* title) const override;
+  bool GetFilename(base::FilePath* path) const override;
+  bool GetFilenames(std::vector<FileInfo>* filenames) const override;
+  bool GetPickledData(const OSExchangeData::CustomFormat& format,
+                      Pickle* data) const override;
+  bool GetFileContents(base::FilePath* filename,
+                       std::string* file_contents) const override;
+  bool GetHtml(base::string16* html, GURL* base_url) const override;
+  bool HasString() const override;
+  bool HasURL(OSExchangeData::FilenameToURLPolicy policy) const override;
+  bool HasFile() const override;
+  bool HasFileContents() const override;
+  bool HasHtml() const override;
+  bool HasCustomFormat(
+      const OSExchangeData::CustomFormat& format) const override;
+  void SetDownloadFileInfo(
+      const OSExchangeData::DownloadFileInfo& download_info) override;
+  void SetDragImage(const gfx::ImageSkia& image,
+                    const gfx::Vector2d& cursor_offset) override;
+  const gfx::ImageSkia& GetDragImage() const override;
+  const gfx::Vector2d& GetDragImageOffset() const override;
 
  private:
   scoped_refptr<DataObjectImpl> data_;
   base::win::ScopedComPtr<IDataObject> source_object_;
 
   // Drag image and offset data. Only used for Ash.
   gfx::ImageSkia drag_image_;
   gfx::Vector2d drag_image_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeDataProviderWin);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_WIN_H_