Sort video capture devices.

CFMs currently rely on this behavior. It was removed in
https://chromium-review.googlesource.com/c/chromium/src/+/2306918.

BUG=b:167805373
TEST='Locally checked order of video capture devices on CFM devices.'

Change-Id: I2dc348a88b6821e7cac257ecf9710ec1c5247942
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2573196Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Auto-Submit: Chris Buquicchio <cbuquicchio@google.com>
Commit-Queue: Chris Buquicchio <cbuquicchio@google.com>
Cr-Commit-Position: refs/heads/master@{#833774}

media/capture/video/linux/video_capture_device_factory_linux.cc

@@ -37,6 +37,11 @@ namespace media {
 
 namespace {
 
+bool CompareCaptureDevices(const VideoCaptureDeviceInfo& a,
+                           const VideoCaptureDeviceInfo& b) {
+  return a.descriptor < b.descriptor;
+}
+
 // USB VID and PID are both 4 bytes long.
 const size_t kVidPidSize = 4;
 const size_t kMaxInterfaceNameSize = 256;
@@ -242,6 +247,10 @@ void VideoCaptureDeviceFactoryLinux::GetDevicesInfo(
     }
   }
 
+  // This is required for some applications that rely on the stable ordering of
+  // devices.
+  std::sort(devices_info.begin(), devices_info.end(), CompareCaptureDevices);
+
   std::move(callback).Run(std::move(devices_info));
 }