Make MediaSession available on Desktop

content/browser/media/media_web_contents_observer.h

Index: content/browser/media/media_web_contents_observer.h
diff --git a/content/browser/media/media_web_contents_observer.h b/content/browser/media/media_web_contents_observer.h
index 5d6d8d2f5ff92d2f54f53bafcd1e03aa7642cab7..e1aa80c66c192d9161f09db345763faa2cc13353 100644
--- a/content/browser/media/media_web_contents_observer.h
+++ b/content/browser/media/media_web_contents_observer.h
@@ -11,6 +11,7 @@
 #include <memory>
 #include <set>
 
+#include "base/containers/scoped_ptr_hash_map.h"
 #include "base/macros.h"
 #include "content/browser/media/session/media_session_controllers_manager.h"
 #include "content/common/content_export.h"
@@ -30,6 +31,8 @@ enum class MediaContentType;
 
 namespace content {
 
+class BrowserMediaSessionManager;
+
 // This class manages all RenderFrame based media related managers at the
 // browser side. It receives IPC messages from media RenderFrameObservers and
 // forwards them to the corresponding managers. The managers are responsible
@@ -39,6 +42,18 @@ class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
   explicit MediaWebContentsObserver(WebContents* web_contents);
   ~MediaWebContentsObserver() override;
 
+  // Gets the BrowserMediaSessionManager associated with the given
+  // |render_frame_host|.  Creates a new one if it doesn't exist. The caller
+  // doesn't own the returned pointer.
+  BrowserMediaSessionManager* GetMediaSessionManager(
+      RenderFrameHost* render_frame_host);
+
+  // Sets or overrides the BrowserMediaSessionManager for the given
+  // |render_frame_host|.
+  void SetMediaSessionManagerForTest(
+      RenderFrameHost* render_frame_host,
+      std::unique_ptr<BrowserMediaSessionManager> manager);
+
   // Called by WebContentsImpl when the audible state may have changed.
   void MaybeUpdateAudibleState();
 
@@ -109,6 +124,12 @@ class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
 
   MediaSessionControllersManager session_controllers_manager_;
 
+  // Map from RenderFrameHost* to BrowserMediaSessionManager.
+  using MediaSessionManagerMap =
+      base::ScopedPtrHashMap<RenderFrameHost*,
+                             std::unique_ptr<BrowserMediaSessionManager>>;
+  MediaSessionManagerMap media_session_managers_;
+
   DISALLOW_COPY_AND_ASSIGN(MediaWebContentsObserver);
 };