[Mojo Video Capture] Simplify API and some cleanups

services/video_capture/public/interfaces/BUILD.gn

 # Copyright 2016 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("interfaces") {
   sources = [
     "mock_video_capture_device.mojom",
+    "video_capture_device_descriptor.mojom",
     "video_capture_device_factory.mojom",
     "video_capture_device_proxy.mojom",
     "video_capture_service.mojom",
+    "video_capture_settings.mojom",
     "video_frame_receiver.mojom",
   ]
 
   deps = [
     "//media/capture/mojo:capture_types",
     "//media/mojo/interfaces",
     "//ui/gfx/geometry/mojo",
   ]
 }