Tab Audio Capture: Browser-side connect/disconnect functionality.

content/browser/renderer_host/media/web_contents_capture_util.h

+// Copyright (c) 2012 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_RENDERER_HOST_MEDIA_WEB_CONTENTS_CAPTURE_UTIL_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_CAPTURE_UTIL_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace content {
+
+class WebContents;
+
+class WebContentsCaptureUtil {
+ public:
+  // Tracks RenderView changes during the lifetime of a WebContents.
+  class RenderViewTracker
+      : public base::RefCountedThreadSafe<RenderViewTracker>,
+        public WebContentsObserver {
+   public:
+    RenderViewTracker();
+
+    // Callback for whenever a new RenderView is swapped in.  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.
+    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.
+    void Stop();
+
+   private:
+    friend class base::RefCountedThreadSafe<RenderViewTracker>;
+
+    virtual ~RenderViewTracker();
+
+    // Reads the render_process_id/render_view_id from the current WebContents
+    // instance and then invokes the callback.
+    void OnWebContentsChangeEvent();
+
+    // 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);
+
+    // How WebContents notifies us of a new RenderView target.
+    virtual void RenderViewReady() OVERRIDE;
+
+    // Called when a WebContents has been destroyed.  This invokes the callback
+    // with MSG_ROUTING_NONE values to indicate tracking will not continue.
+    virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
+
+    base::Lock lock_;  // Guards changes to callback_.
+    ChangeCallback callback_;
+  };
+
+  // Function to extract the target renderer id's from a tab media stream
+  // request's device id.
+  static bool ExtractTabCaptureTarget(const std::string& device_id,
+                                      int* render_process_id,
+                                      int* render_view_id);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_CAPTURE_UTIL_H_