Do not use libv4l if no plugin is registered.

content/common/gpu/media/generic_v4l2_device.h

Index: content/common/gpu/media/generic_v4l2_device.h
diff --git a/content/common/gpu/media/generic_v4l2_device.h b/content/common/gpu/media/generic_v4l2_device.h
index 94d656c65ce58d46c396985b3a57b9eb20490f93..4a084c178466b1abe35bd86e9856f64b7d18dff9 100644
--- a/content/common/gpu/media/generic_v4l2_device.h
+++ b/content/common/gpu/media/generic_v4l2_device.h
@@ -8,6 +8,7 @@
 #ifndef CONTENT_COMMON_GPU_MEDIA_GENERIC_V4L2_DEVICE_H_
 #define CONTENT_COMMON_GPU_MEDIA_GENERIC_V4L2_DEVICE_H_
 
+#include "base/files/scoped_file.h"
 #include "content/common/gpu/media/v4l2_device.h"
 
 namespace content {
@@ -46,11 +47,14 @@ class GenericV4L2Device : public V4L2Device {
   const Type type_;
 
   // The actual device fd.
-  int device_fd_;
+  base::ScopedFD device_fd_;
 
   // eventfd fd to signal device poll thread when its poll() should be
   // interrupted.
-  int device_poll_interrupt_fd_;
+  base::ScopedFD device_poll_interrupt_fd_;
+
+  // Use libv4l2 when operating |device_fd_|.
+  bool use_libv4l2_;
 
   DISALLOW_COPY_AND_ASSIGN(GenericV4L2Device);