Adds hook for content embedders to get media::BrowserCdm*.

content/browser/media/cdm/browser_cdm_manager.h

 // Copyright 2014 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 CONTENT_BROWSER_MEDIA_CDM_BROWSER_CDM_MANAGER_H_
 #define CONTENT_BROWSER_MEDIA_CDM_BROWSER_CDM_MANAGER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 32 matching lines @@
   // all messages are posted to the browser UI thread.
   BrowserCdmManager(int render_process_id,
                     const scoped_refptr<base::TaskRunner>& task_runner);
 
   // BrowserMessageFilter implementations.
   void OnDestruct() const override;
   base::TaskRunner* OverrideTaskRunnerForMessage(
       const IPC::Message& message) override;
   bool OnMessageReceived(const IPC::Message& message) override;
 
-  media::BrowserCdm* GetCdm(int render_frame_id, int cdm_id);
+  media::BrowserCdm* GetCdm(int render_frame_id, int cdm_id) const;
 
   // Notifies that the render frame has been deleted so that all CDMs belongs
   // to this render frame needs to be destroyed as well. This is needed because
   // in some cases (e.g. fast termination of the renderer), the message to
   // destroy the CDM will not be received.
   void RenderFrameDeleted(int render_frame_id);
 
   // Promise handlers.
   void ResolvePromise(int render_frame_id, int cdm_id, uint32_t promise_id);
   void ResolvePromiseWithSession(int render_frame_id,
@@ skipping 120 matching lines @@
   std::map<uint64, base::Closure> cdm_cancel_permission_map_;
 
   base::WeakPtrFactory<BrowserCdmManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserCdmManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_CDM_BROWSER_CDM_MANAGER_H_