Begin adding support for tab mirroring via the MediaStream audio/video capturing

content/public/common/media_stream_request.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_PUBLIC_COMMON_MEDIA_STREAM_REQUEST_H_
 #define CONTENT_PUBLIC_COMMON_MEDIA_STREAM_REQUEST_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "content/common/content_export.h"
 #include "googleurl/src/gurl.h"
 
 namespace content {
 
 // Types of media streams.
 enum MediaStreamDeviceType {
-  MEDIA_STREAM_DEVICE_TYPE_NO_SERVICE = 0,
-  MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE,
-  MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE,
-  NUM_MEDIA_STREAM_DEVICE_TYPES
+  MEDIA_NO_SERVICE = 0,
+
+  // A user device provided by the operating system (e.g., webcam input).
+  MEDIA_USER_AUDIO_CAPTURE,
+  MEDIA_USER_VIDEO_CAPTURE,

[wjia(left Chromium), 2012/09/03 15:54:17]

"user" states ownership, not the type of input streams. Please use a better name
if "device" is not deemed appropriate. Note that when
MEDIA_STREAM_DEVICE_TYPE_*_CAPTURE is used, it's targeting physical local
capture devices. 

[miu, 2012/09/04 20:42:19]

I see your point.  My original intention was that "user" referred to
user-generated content (webcam, microphone, etc.).

I've changed them to MEDIA_AUDIO_DEVICE_CAPTURE and MEDIA_VIDEO_DEVICE_CAPTURE.

+
+  // Mirroring of a browser tab.
+  MEDIA_TAB_AUDIO_CAPTURE,
+  MEDIA_TAB_VIDEO_CAPTURE,
+
+  NUM_MEDIA_TYPES
 };
 
+// Convenience predicates to determine whether the given type represents some
+// audio or some video device.
+CONTENT_EXPORT bool IsAudioMediaType(MediaStreamDeviceType type);
+CONTENT_EXPORT bool IsVideoMediaType(MediaStreamDeviceType type);
+
 // TODO(xians): Change the structs to classes.
 // Represents one device in a request for media stream(s).
 struct CONTENT_EXPORT MediaStreamDevice {
   MediaStreamDevice(
       MediaStreamDeviceType type,
       const std::string& device_id,
       const std::string& name);
 
   ~MediaStreamDevice();
 
@@ skipping 32 matching lines @@
 
   // A list of devices present on the user's computer, for each device type
   // requested.
   // All the elements in this map will be deleted in ~MediaStreamRequest().
   MediaStreamDeviceMap devices;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_COMMON_MEDIA_STREAM_REQUEST_H_