drm: GPU process manages VGEM fd.

ui/ozone/platform/drm/host/drm_device_handle.cc

 // Copyright 2015 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 "ui/ozone/platform/drm/host/drm_device_handle.h"
 
 #include <fcntl.h>
 #include <xf86drm.h>
 #include <xf86drmMode.h>
 
 #include "base/files/file_path.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/threading/thread_restrictions.h"
 
 namespace ui {
 
 namespace {
 
 bool Authenticate(int fd) {
   drm_magic_t magic;
   memset(&magic, 0, sizeof(magic));
   // We need to make sure the DRM device has enough privilege. Use the DRM
   // authentication logic to figure out if the device has enough permissions.
   return !drmGetMagic(fd, &magic) && !drmAuthMagic(fd, magic);
 }
 
 }  // namespace
 
-DrmDeviceHandle::DrmDeviceHandle() {
+DrmDeviceHandle::DrmDeviceHandle() : is_vgem_(false) {
 }
 
 DrmDeviceHandle::~DrmDeviceHandle() {
   if (file_.is_valid())
     base::ThreadRestrictions::AssertIOAllowed();
 }
 
-bool DrmDeviceHandle::Initialize(const base::FilePath& path) {
+bool DrmDeviceHandle::Initialize(const base::FilePath& path, bool is_vgem) {
   CHECK(path.DirName() == base::FilePath("/dev/dri"));
   base::ThreadRestrictions::AssertIOAllowed();
+  is_vgem_ = is_vgem;
   bool print_warning = true;
   while (true) {
     file_.reset();
     int fd = HANDLE_EINTR(open(path.value().c_str(), O_RDWR | O_CLOEXEC));
     if (fd < 0) {
       PLOG(ERROR) << "Failed to open " << path.value();
       return false;
     }
 
     file_.reset(fd);
+    if (is_vgem_)
+      break;
 
     if (Authenticate(file_.get()))
       break;
 
     LOG_IF(WARNING, print_warning) << "Failed to authenticate " << path.value();
     print_warning = false;
     usleep(100000);
   }
 
   VLOG(1) << "Succeeded authenticating " << path.value();
   return true;
 }
 
 bool DrmDeviceHandle::IsValid() const {
   return file_.is_valid();
 }
 
 base::ScopedFD DrmDeviceHandle::PassFD() {
   return file_.Pass();
 }
 
 }  // namespace ui