ImageCapture: Implement TakePhoto() for Linux/CrOs

media/capture/video/linux/video_capture_device_linux.cc

 // Copyright (c) 2012 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.
 
 #include "media/capture/video/linux/video_capture_device_linux.h"
 
 #include <stddef.h>
 
 #include <list>
 
@@ skipping 61 matching lines @@
 }
 
 void VideoCaptureDeviceLinux::StopAndDeAllocate() {
   if (!v4l2_thread_.IsRunning())
     return;  // Wrong state.
   v4l2_thread_.task_runner()->PostTask(
       FROM_HERE,
       base::Bind(&V4L2CaptureDelegate::StopAndDeAllocate, capture_impl_));
   v4l2_thread_.Stop();
 
   capture_impl_ = NULL;

[mcasas, 2016/09/16 03:50:37]

nit: not your code, but can you s/NULL/nullptr/ plz?

[xianglu, 2016/09/16 18:22:34]

Done.

 }
 
+void VideoCaptureDeviceLinux::TakePhoto(TakePhotoCallback callback) {
+  DCHECK(capture_impl_);
+  DCHECK(v4l2_thread_.IsRunning());

[mcasas, 2016/09/16 03:50:37]

This should be a 
if (!v4l2_thread_.IsRunning())
  return;

otherwise when DCHECK()s are disconnected
(i.e. in a Release build), we'd crash in l.90.

[xianglu, 2016/09/16 18:22:34]

Done.

+  DVLOG(1) << "in VCDLinux: TakePhoto() is called";

[mcasas, 2016/09/16 03:50:37]

nit: Remove this. In any case, it should be
before the DCHECK()s (so if they are hit, you'd
still see something), and using __func__:

DVLOG(1) << __func__;

[xianglu, 2016/09/16 18:22:34]

Done.

+
+  v4l2_thread_.task_runner()->PostTask(
+      FROM_HERE, base::Bind(&V4L2CaptureDelegate::TakePhoto, capture_impl_,
+                            base::Passed(&callback)));
+}
+
 void VideoCaptureDeviceLinux::SetRotation(int rotation) {
   if (v4l2_thread_.IsRunning()) {
     v4l2_thread_.task_runner()->PostTask(
         FROM_HERE,
         base::Bind(&V4L2CaptureDelegate::SetRotation, capture_impl_, rotation));
   }
 }
 
 // static
 int VideoCaptureDeviceLinux::TranslatePowerLineFrequencyToV4L2(
     PowerLineFrequency frequency) {
   switch (frequency) {
     case media::PowerLineFrequency::FREQUENCY_50HZ:
       return V4L2_CID_POWER_LINE_FREQUENCY_50HZ;
     case media::PowerLineFrequency::FREQUENCY_60HZ:
       return V4L2_CID_POWER_LINE_FREQUENCY_60HZ;
     default:
       // If we have no idea of the frequency, at least try and set it to AUTO.
       return V4L2_CID_POWER_LINE_FREQUENCY_AUTO;
   }
 }
 
 }  // namespace media