Media Remoting: Data/Control plumbing between renderer and Media Router.

chrome/browser/media/cast_remoting_connector.h

+// Copyright 2016 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_BROWSER_MEDIA_CAST_REMOTING_CONNECTOR_H_
+#define CHROME_BROWSER_MEDIA_CAST_REMOTING_CONNECTOR_H_
+
+#include <set>
+
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/media/router/media_routes_observer.h"
+#include "chrome/browser/media/router/route_message.h"
+#include "content/public/browser/web_contents_user_data.h"
+#include "media/mojo/interfaces/remoting.mojom.h"
+
+namespace content {
+class RenderFrameHost;
+}
+
+// CastRemotingConnector connects a single source (a media element in a render
+// frame) with a single sink (a media player in a remote device). There is one
+// instance of a CastRemotingConnector per source WebContents (representing a
+// collection of render frames), and it is created on-demand. The source in the
+// render process represents itself by providing a media::mojom::RemotingSource
+// service instance. The sink is represented by the Media Router Cast Provider.
+//
+// Whenever a RenderFrameHost is created, ChromeContentBrowserClient will call
+// CreateRemoterFactory() to instantiate an implementation of
+// media::mojom::RemoterFactory associated with the connector. This allows one
+// or more media sources in a render frame to create a media::mojom::Remoter to
+// start/stop and execute media remoting. Media sources also provide a
+// media::mojom::RemotingSource so that the connector may notify them when a
+// sink becomes available for remoting and pass binary messages from the sink
+// back to the source.
+//
+// At any time before or after the CastRemotingConnector is created, the
+// Media Router Cast Provider may create a tab remoting media route. This
+// indicates that the provider has found a sink that is capable of remoting and
+// is available for use. At this point, CastRemotingConnector notifies all
+// RemotingSources that a sink is available, and some time later a
+// RemotingSource can request the start of a remoting session. Once the sink is
+// no longer available, the provider terminates the route and
+// CastRemotingConnector notifies all RemotingSources that the sink is gone.
+//
+// Note that only one RemotingSource can remote media at a time. Therefore,
+// CastRemotingConnector must mitigate among simultaneous requests for media
+// remoting, and only allow one at a time. Currently, the policy is "first come,
+// first served."
+//
+// When starting a remoting session, the CastRemotingConnector sends control
+// messages to the Cast Provider. These control messages direct the provider to
+// start/stop remoting with the remote device (e.g., launching apps or services
+// on the remote device). Among its other duties, the provider will also set up
+// a Cast Streaming session to provide a bitstream transport for the media. Once
+// this is done, the provider sends notification messages back to
+// CastRemotingConnector to acknowledge this. Then, CastRemotingConnector knows
+// it can look-up and pass the mojo data pipe handles to CastRemotingSenders,
+// and the remoting session will be fully active. The CastRemotingConnector is
+// responsible for passing small binary messages between the source and sink,
+// while the CastRemotingSender handles the high-volume media data transfer.
+//
+// Please see the unit tests in cast_remoting_connector_unittest.cc as a
+// reference for how CastRemotingConnector and a Cast Provider interact to
+// start/execute/stop remoting sessions.
+class CastRemotingConnector
+    : protected content::WebContentsUserData<CastRemotingConnector>,
+      public media_router::MediaRoutesObserver {
+ public:
+  // Returns the instance of the CastRemotingConnector associated with
+  // |source_contents|, creating a new instance if needed.
+  static CastRemotingConnector* Get(content::WebContents* source_contents);
+
+  // Used by ChromeContentBrowserClient to request a binding to a new
+  // RemoterFactory for each new render frame. The |render_frame_host| is
+  // expected to outlive the mojo message pipe in |request| that the service
+  // binds to.
+  static void CreateRemoterFactory(content::RenderFrameHost* render_frame_host,
+                                   media::mojom::RemoterFactoryRequest request);
+
+ protected:
+  friend class content::WebContentsUserData<CastRemotingConnector>;
+
+  // Constructor used only by WebContentsUserData.
+  explicit CastRemotingConnector(content::WebContents* source_contents);
+
+  ~CastRemotingConnector() final;
+
+ private:
+  // Allow unit tests access to the private constructor and CreateBridge()
+  // method, since unit tests don't have a complete browser (i.e., with a
+  // WebContents and RenderFrameHost) to work with.
+  friend class CastRemotingConnectorTest;
+
+  // Implementation of the media::mojom::RemoterFactory, with one instance
+  // created per content::RenderFrameHost. An instance of this class is owned by
+  // its mojo message pipe.
+  class FrameRemoterFactory;
+
+  // Implementation of the media::mojom::Remoter service for a single source in
+  // a render frame. This is just a "lightweight bridge" that delegates calls
+  // back-and-forth between a CastRemotingConnector and a
+  // media::mojom::RemotingSource. An instance of this class is owned by its
+  // mojo message pipe.
+  class RemotingBridge;
+
+  // A RouteMessageObserver for the remoting route that passes messages from the
+  // Cast Provider back to this connector. An instance of this class only exists
+  // while a remoting route is available, and is owned by CastRemotingConnector.
+  class MessageObserver;
+
+  // Main constructor. |route_source_id| is the remoting route source specific
+  // to one tab (WebContents).
+  CastRemotingConnector(media_router::MediaRouter* router,
+                        const media_router::MediaSource::Id& route_source_id);
+
+  // Creates a RemotingBridge that implements the requested Remoter service, and
+  // binds it to the interface |request|.
+  void CreateBridge(media::mojom::RemotingSourcePtr source,
+                    media::mojom::RemoterRequest request);
+
+  // Called by the RemotingBridge constructor/destructor to register/deregister
+  // an instance. This allows this connector to broadcast notifications to all
+  // active sources.
+  void RegisterBridge(RemotingBridge* bridge);
+  void DeregisterBridge(RemotingBridge* bridge,
+                        media::mojom::RemotingStopReason reason);
+
+  // These methods are called by RemotingBridge to forward media::mojom::Remoter
+  // calls from a source through to this connector. They ensure that only one
+  // source is allowed to be in a remoting session at a time, and that no source
+  // may interfere with any other.
+  void StartRemoting(RemotingBridge* bridge);
+  void StartRemotingDataStreams(
+      RemotingBridge* bridge,
+      mojo::ScopedDataPipeConsumerHandle audio_pipe,
+      mojo::ScopedDataPipeConsumerHandle video_pipe,
+      media::mojom::RemotingDataStreamSenderRequest audio_sender_request,
+      media::mojom::RemotingDataStreamSenderRequest video_sender_request);
+  void StopRemoting(RemotingBridge* bridge,
+                    media::mojom::RemotingStopReason reason);
+  void SendMessageToSink(RemotingBridge* bridge,
+                         const std::vector<uint8_t>& message);
+
+  // Send a control message to the Cast Provider. This may or may not succeed,
+  // with the success status reported later via HandleSendMessageResult().
+  void SendMessageToProvider(const std::string& message);
+
+  // Called by the current MessageObserver to process messages observed on the
+  // remoting route. There are two types of messages: 1) TEXT notification
+  // messages from the Cast Provider, to report on the current state of a
+  // remoting session between Chrome and the remote device, and 2) BINARY
+  // messages, to be passed directly to the active remoting source during a
+  // remoting session.
+  void ProcessMessagesFromRoute(
+      const std::vector<media_router::RouteMessage>& messages);
+
+  // Error handlers for message/data sending during an active remoting
+  // session. When a failure occurs, these immediately force-stop remoting.
+  void HandleSendMessageResult(bool success);
+  void OnDataSendFailed();
+
+  // MediaRoutesObserver implementation: Scans |routes| to check whether the
+  // existing remoting route has gone away and/or there is a new remoting route
+  // established, and take the necessary actions to notify sources and/or
+  // shutdown an active remoting session.
+  void OnRoutesUpdated(
+      const std::vector<media_router::MediaRoute>& routes,
+      const std::vector<media_router::MediaRoute::Id>& ignored) final;
+
+  // Set of registered RemotingBridges, maintained by RegisterBridge() and
+  // DeregisterBridge(). These pointers are always valid while they are in this
+  // set.
+  std::set<RemotingBridge*> bridges_;
+
+  // Created when the Media Router Cast Provider has created a media remoting
+  // route to a sink that supports remoting and is available for use. This
+  // observer simply dispatches messages from the Cast Provider and sink back to
+  // this connector. Once the route is gone, this is reset to null.
+  std::unique_ptr<MessageObserver> message_observer_;
+
+  // Incremented each time StartRemoting() is called, and used as a "current
+  // session ID" to ensure that control messaging between this connector and the
+  // Cast Provider are referring to the same remoting session. This allows both
+  // this connector and the provider to ignore stale messages.
+  unsigned int session_counter_;
+
+  // When non-null, an active remoting session is taking place, with this
+  // pointing to the RemotingBridge being used to communicate with the source.
+  RemotingBridge* active_bridge_;
+
+  // These temporarily hold the mojo data pipe handles and interface requests
+  // until hand-off to the CastRemotingSenders.
+  mojo::ScopedDataPipeConsumerHandle pending_audio_pipe_;
+  mojo::ScopedDataPipeConsumerHandle pending_video_pipe_;
+  media::mojom::RemotingDataStreamSenderRequest pending_audio_sender_request_;
+  media::mojom::RemotingDataStreamSenderRequest pending_video_sender_request_;
+
+  // Produces weak pointers that are only valid for the current remoting
+  // session. This is used to cancel any outstanding callbacks when a remoting
+  // session is stopped.
+  base::WeakPtrFactory<CastRemotingConnector> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(CastRemotingConnector);
+};
+
+#endif  // CHROME_BROWSER_MEDIA_CAST_REMOTING_CONNECTOR_H_