Tab Audio Mirroring: WebContentsAudioInputStream is a new implementation which represents the lifet…

content/browser/renderer_host/media/web_contents_tracker.h

+// Copyright (c) 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.
+//
+// Given a starting render_process_id and render_view_id, the WebContentsTracker
+// tracks RenderViewHost instance swapping during the lifetime of a WebContents
+// instance.  This is used when mirroring tab video and audio so that user
+// navigations, crashes, etc., during a tab's lifetime allow the capturing code
+// to remain active on the current/latest RenderView.
+//
+// Threading issues: Start(), Stop() and the ChangeCallback are invoked on the
+// same thread.  This can be any thread, and the decision is locked-in by
+// WebContentsTracker when Start() is called.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_TRACKER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_TRACKER_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace content {
+
+class CONTENT_EXPORT WebContentsTracker
+    : public base::RefCountedThreadSafe<WebContentsTracker>,
+      public WebContentsObserver {
+ public:
+  WebContentsTracker();
+
+  // Callback for whenever the target is swapped.  The callback is also invoked
+  // with both arguments set to MSG_ROUTING_NONE to indicate tracking will not
+  // continue (i.e., the WebContents instance was not found or has been
+  // destroyed).
+  typedef base::Callback<void(int render_process_id, int render_view_id)>
+      ChangeCallback;
+
+  // Start tracking.  The last-known |render_process_id| and |render_view_id|
+  // are provided, and the given callback is invoked asynchronously one or more
+  // times.  The callback will be invoked on the same thread calling Start().
+  virtual void Start(int render_process_id, int render_view_id,
+                     const ChangeCallback& callback);
+
+  // Stop tracking.  Once this method returns, the callback is guaranteed not to
+  // be invoked again.
+  virtual void Stop();
+
+ protected:
+  friend class base::RefCountedThreadSafe<WebContentsTracker>;
+  virtual ~WebContentsTracker();
+
+ private:
+  // Reads the render_process_id/render_view_id from the current WebContents
+  // instance and then invokes the callback.
+  void OnWebContentsChangeEvent();
+
+  // Called on the thread that Start()/Stop() are called on, check whether the
+  // callback is still valid and, if so, invoke it.
+  void MaybeDoCallback(int render_process_id, int render_view_id);
+
+  // Look-up the current WebContents instance associated with the given
+  // |render_process_id| and |render_view_id| and begin observing it.
+  void LookUpAndObserveWebContents(int render_process_id,
+                                   int render_view_id);
+
+  // WebContentsObserver overrides to react to events of interest.
+  virtual void RenderViewReady() OVERRIDE;
+  virtual void AboutToNavigateRenderView(RenderViewHost* render_view_host)
+      OVERRIDE;
+  virtual void DidNavigateMainFrame(const LoadCommittedDetails& details,
+                                    const FrameNavigateParams& params) OVERRIDE;
+  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
+
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
+  ChangeCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebContentsTracker);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_TRACKER_H_