[Mojo Video Capture] Simplify API and some cleanups

services/video_capture/public/interfaces/video_capture_settings.mojom

+// 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.
+
+module video_capture.mojom;
+
+import "media/capture/mojo/video_capture_types.mojom";
+import "ui/gfx/geometry/mojo/geometry.mojom";
+
+// This format implies a pixel format of I420
+// and a storage type of Mojo Shared Memory.
+struct VideoCaptureFormat {
+  gfx.mojom.Size frame_size;
+  float frame_rate;
+};
+
+struct VideoCaptureSettings {
+  VideoCaptureFormat format;
+  media.mojom.ResolutionChangePolicy resolution_change_policy;
+  media.mojom.PowerLineFrequency power_line_frequency;
+};