Video Capture Mojo Component: Skeleton

device/video/video_capture_device.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 device.mojom;
+
+import "device/video/video_capture_device_client.mojom";
+import "device/video/video_capture_format.mojom";
+
+enum ResolutionChangePolicy {
+  FIXED_RESOLUTION,
+  FIXED_ASPECT_RATIO,
+  ANY_WITHIN_LIMIT,
+};
+
+enum PowerLineFrequency {
+  FREQUENCY_DEFAULT,
+  FREQUENCY_50HZ,
+  FREQUENCY_60HZ

[mcasas, 2016/08/02 22:18:09]

Same applies here: no need for FREQUENCY_
prefix

[Ken Rockot(use gerrit already), 2016/08/02 22:46:25]

Unfortunately "50HZ" isn't a valid symbol name either. Though a shorter prefix
on those would be fine (F_50HZ?), and DEFAULT can be prefix-free.

[chfremer, 2016/08/03 22:14:14]

I am going with HZ_50, because I want to avoid using a prefix "F" that might
make the reader think there is some meaning to it where there is none.

+};
+
+struct VideoCaptureParams {

[Ken Rockot(use gerrit already), 2016/08/02 22:46:25]

There's little value in defining a struct here if it's just used as an argument
to a single function. These fields should just be arguments to AllocateAndStart.

[chfremer, 2016/08/03 22:14:14]

Good point. Initially I was planning to keep the interface as close to the C++
version as possible to make it easier to see the correspondence during reviews.
But it seems that the Mojo mechanics and conventions are different enough to
warrant adapting the interfaces already in this step.

Done.

+  VideoCaptureFormat requested_format;
+  ResolutionChangePolicy resolution_change_policy;
+  PowerLineFrequency power_line_frequency;
+};
+
+interface VideoCaptureDevice {
+  AllocateAndStart(VideoCaptureParams requested_config,

[Ken Rockot(use gerrit already), 2016/08/02 22:46:25]

nit: Maybe "Allocate" is an unnecessary detail? Just "Start()?"

[chfremer, 2016/08/03 22:14:14]

Done.

+                   VideoCaptureDeviceClient client);
+  StopAndDeAllocate();

[Ken Rockot(use gerrit already), 2016/08/02 22:46:25]

How about the impl just treats VideoCaptureDevice pipe closure as the signal to
"stop and deallocate". It has to do that anyway when the pipe is closed, so
adding a request for the same behavior seems unnecessary.

[chfremer, 2016/08/03 22:14:14]

Agreed, assuming that each VideoCaptureDevice instance can only be started and
stopped once, which is probably the case.

Done.

+};