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 */)
+
+// 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 */)