[Ozone-DRI] Allow initialization with no displays

ui/ozone/platform/dri/screen_manager.cc

 // 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.
 
 #include "ui/ozone/platform/dri/screen_manager.h"
 
 #include <xf86drmMode.h>
 
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/rect.h"
@@ skipping 136 matching lines @@
   }
 
   return controllers_.end();
 }
 
 void ScreenManager::ForceInitializationOfPrimaryDisplay() {
   LOG(WARNING) << "Forcing initialization of primary display.";
   ScopedVector<HardwareDisplayControllerInfo> displays =
       GetAvailableDisplayControllerInfos(dri_->get_fd());
 
-  DCHECK_NE(0u, displays.size());
+  if (displays.empty())
+    return;
 
   ScopedDrmPropertyPtr dpms(
       dri_->GetProperty(displays[0]->connector(), "DPMS"));
   if (dpms)
     dri_->SetProperty(displays[0]->connector()->connector_id,
                       dpms->prop_id,
                       DRM_MODE_DPMS_ON);
 
   AddDisplayController(dri_,
                        displays[0]->crtc()->crtc_id,
@@ skipping 41 matching lines @@
 
   // When things go wrong revert back to the previous configuration since
   // it is expected that the configuration would not have changed if
   // things fail.
   (*original)->AddCrtc((*mirror)->RemoveCrtc(crtc));
   (*original)->Enable();
   return false;
 }
 
 }  // namespace ui