[spelling] existance to existence

chrome/installer/util/scoped_user_protocol_entry.h

 // Copyright 2015 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 CHROME_INSTALLER_UTIL_SCOPED_USER_PROTOCOL_ENTRY_H_
 #define CHROME_INSTALLER_UTIL_SCOPED_USER_PROTOCOL_ENTRY_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 
 class RegistryEntry;
 
 // Windows 8 shows the "No apps are installed to open this type of link"
 // dialog when choosing a default handler for a |protocol| under certain
 // circumstances. Under these circumstances, it appears that ensuring the
-// existance of the HKCU\Software\Classes\<protocol> key with an empty "URL
+// existence of the HKCU\Software\Classes\<protocol> key with an empty "URL
 // Protocol" value is sufficient to make the dialog contain the usual list of
 // registered browsers. This class creates this key and value in its constructor
 // if needed, and cleans them up in its destructor if no other values or subkeys
 // were created in the meantime. For details, see https://crbug.com/569151.
 class ScopedUserProtocolEntry {
  public:
   explicit ScopedUserProtocolEntry(const wchar_t* protocol);
   ~ScopedUserProtocolEntry();
 
  private:
   std::vector<std::unique_ptr<RegistryEntry>> entries_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedUserProtocolEntry);
 };
 
 #endif  // CHROME_INSTALLER_UTIL_SCOPED_USER_PROTOCOL_ENTRY_H_