Support external buffer import in VDA interface and add a V4L2SVDA impl.

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 3e52fa933866b180aa6dc540ab1a3cd403ed8c49..a5f787b0ee089d077c2ef8b5b482baf619173d05 100644
--- a/content/common/gpu/media/generic_v4l2_device.h
+++ b/content/common/gpu/media/generic_v4l2_device.h
@@ -33,14 +33,22 @@ class GenericV4L2Device : public V4L2Device {
              unsigned int offset) override;
   void Munmap(void* addr, unsigned int len) override;
   bool Initialize() override;
+
+  std::vector<base::ScopedFD> GetDmabufsForV4L2Buffer(
+      int index,
+      size_t num_planes,
+      enum v4l2_buf_type type) override;
+
   bool CanCreateEGLImageFrom(uint32_t v4l2_pixfmt) override;
-  EGLImageKHR CreateEGLImage(EGLDisplay egl_display,
-                             EGLContext egl_context,
-                             GLuint texture_id,
-                             gfx::Size frame_buffer_size,
-                             unsigned int buffer_index,
-                             uint32_t v4l2_pixfmt,
-                             size_t num_v4l2_planes) override;
+  EGLImageKHR CreateEGLImage(
+      EGLDisplay egl_display,
+      EGLContext egl_context,
+      GLuint texture_id,
+      const gfx::Size& size,
+      unsigned int buffer_index,
+      uint32_t v4l2_pixfmt,
+      const std::vector<base::ScopedFD>& dmabuf_fds) override;
+
   EGLBoolean DestroyEGLImage(EGLDisplay egl_display,
                              EGLImageKHR egl_image) override;
   GLenum GetTextureTarget() override;