support video device enumeration from renderer process.

content/common/media/media_stream_messages.h

Index: content/common/media/media_stream_messages.h
===================================================================
--- content/common/media/media_stream_messages.h	(revision 118766)
+++ content/common/media/media_stream_messages.h	(working copy)
@@ -51,6 +51,27 @@
                     std::string /* label */,
                     int /* index */)
 
+// The browser has enumerated devices successfully.
+IPC_MESSAGE_ROUTED2(MediaStreamMsg_DevicesEnumerated,
+                    int /* request id */,
+                    media_stream::StreamDeviceInfoArray /* device_list */)
+
+// The browser has failed to enumerate devices.
+IPC_MESSAGE_ROUTED1(MediaStreamMsg_DevicesEnumerationFailed,
+                    int /* request id */)
+
+// TODO(wjia): should DeviceOpen* messages be merged with
+// StreamGenerat* ones?
+// The browser has opened a device successfully.
+IPC_MESSAGE_ROUTED3(MediaStreamMsg_DeviceOpened,
+                    int /* request id */,
+                    std::string /* label */,
+                    media_stream::StreamDeviceInfo /* the device */)
+
+// The browser has failed to open a device.
+IPC_MESSAGE_ROUTED1(MediaStreamMsg_DeviceOpenFailed,
+                    int /* request id */)
+
 // Messages sent from the renderer to the browser.
 
 // Request a new media stream.
@@ -64,3 +85,18 @@
 IPC_MESSAGE_CONTROL2(MediaStreamHostMsg_StopGeneratedStream,
                      int /* render view id */,
                      std::string /* label */)
+
+// Request to enumerate devices.
+IPC_MESSAGE_CONTROL4(MediaStreamHostMsg_EnumerateDevices,
+                     int /* render view id */,
+                     int /* request id */,
+                     media_stream::MediaStreamType /* type */,
+                     std::string /* security origin */)

[scherkus (not reviewing), 2012/01/25 03:19:42]

OOC how are security origins used in the browser process?

It's not a hard rule or anything but in general code closer to webkit should
care about security origins and hide those details from the browser. For
example, if PPAPI were to use this API -- would they need to fill in the
security origin field?

[wjia(left Chromium), 2012/01/25 22:50:44]

Right now, security origin is not used since the user interface has not been
done yet. I think it will be used for user interface (to get permission from
user to access device).

My understanding is that Pepper would need same user interface to get device
access permission, since not all Pepper clients are trustable.

+
+// Request to open the device.
+IPC_MESSAGE_CONTROL5(MediaStreamHostMsg_OpenDevice,
+                     int /* render view id */,
+                     int /* request id */,
+                     std::string /* device_id */,
+                     media_stream::MediaStreamType /* type */,
+                     std::string /* security origin */)