Do not use libv4l if no plugin is registered.

content/common/gpu/media/generic_v4l2_device.h

 // Copyright 2014 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.
 //
 // This file contains the implementation of GenericV4L2Device used on
 // platforms, which provide generic V4L2 video codec devices.
 
 #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 {
 
 class GenericV4L2Device : public V4L2Device {
  public:
   explicit GenericV4L2Device(Type type);
 
   // V4L2Device implementation.
   int Ioctl(int request, void* arg) override;
@@ skipping 18 matching lines @@
   EGLBoolean DestroyEGLImage(EGLDisplay egl_display,
                              EGLImageKHR egl_image) override;
   GLenum GetTextureTarget() override;
   uint32 PreferredInputFormat() override;
 
  private:
   ~GenericV4L2Device() override;
   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_;

[Pawel Osciak, 2015/04/21 09:19:46]

Ah I realized, this should be under #ifdef USE_LIBV4L2 as well I think?

[wuchengli, 2015/04/21 09:25:24]

v4l2_close and v4l2_ioctl won't compile if USE_LIBV4L2 isn't defined. This one
is fine. So we don't need to add more #ifdef here and the constructor
initialization list. Also technically |use_libv4l2_| == false is correct when
USE_LIBV4L2 is not defined.

 
   DISALLOW_COPY_AND_ASSIGN(GenericV4L2Device);
 
   // Lazily initialize static data after sandbox is enabled.  Return false on
   // init failure.
   static bool PostSandboxInitialization();
 };
 }  //  namespace content
 
 #endif  // CONTENT_COMMON_GPU_MEDIA_GENERIC_V4L2_DEVICE_H_