Extract requestMediaKeySystemAccess() algorithm.

media/base/key_systems.h

 // Copyright 2013 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 MEDIA_BASE_KEY_SYSTEMS_H_
 #define MEDIA_BASE_KEY_SYSTEMS_H_
 
 #include <string>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "media/base/eme_constants.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 // Provides an interface for querying registered key systems. The exposed API is
 // only intended to support unprefixed EME.
 //
 // Many of the original static methods are still available, they should be
 // migrated into this interface over time (or removed).
 //
 // TODO(sandersd): Provide GetKeySystem() so that it is not necessary to pass
 // |key_system| to every method. http://crbug.com/457438
 class MEDIA_EXPORT KeySystems {
  public:
-  static KeySystems& GetInstance();
+  static KeySystems* GetInstance();
 
   // Returns whether |key_system| is a supported key system.
   virtual bool IsSupportedKeySystem(const std::string& key_system) const = 0;
 
   // Returns whether |init_data_type| is supported by |key_system|.
   virtual bool IsSupportedInitDataType(
       const std::string& key_system,
       EmeInitDataType init_data_type) const = 0;
 
   // Returns whether the list of codecs are supported together by |key_system|.
@@ skipping 89 matching lines @@
 MEDIA_EXPORT void AddContainerMask(const std::string& container, uint32 mask);
 MEDIA_EXPORT void AddCodecMask(
     EmeMediaType media_type,
     const std::string& codec,
     uint32 mask);
 #endif  // defined(UNIT_TEST)
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_KEY_SYSTEMS_H_