ImageCapture: Implement TakePhoto() for Linux/CrOs

media/capture/video/linux/video_capture_device_linux.cc

Index: media/capture/video/linux/video_capture_device_linux.cc
diff --git a/media/capture/video/linux/video_capture_device_linux.cc b/media/capture/video/linux/video_capture_device_linux.cc
index c6ddd2b070a4d5434102091bb84743dba60046a1..cb12175ab14bb94a57f042f67cf81d265b02af99 100644
--- a/media/capture/video/linux/video_capture_device_linux.cc
+++ b/media/capture/video/linux/video_capture_device_linux.cc
@@ -79,7 +79,16 @@ void VideoCaptureDeviceLinux::StopAndDeAllocate() {
       base::Bind(&V4L2CaptureDelegate::StopAndDeAllocate, capture_impl_));
   v4l2_thread_.Stop();
 
-  capture_impl_ = NULL;
+  capture_impl_ = nullptr;
+}
+
+void VideoCaptureDeviceLinux::TakePhoto(TakePhotoCallback callback) {
+  DCHECK(capture_impl_);
+  if (!v4l2_thread_.IsRunning())
+    return;
+  v4l2_thread_.task_runner()->PostTask(
+      FROM_HERE, base::Bind(&V4L2CaptureDelegate::TakePhoto, capture_impl_,
+                            base::Passed(&callback)));
 }
 
 void VideoCaptureDeviceLinux::SetRotation(int rotation) {