Check that capture_device_ is valid before setting the rotation on it

media/video/capture/linux/video_capture_device_chromeos.cc

Index: media/video/capture/linux/video_capture_device_chromeos.cc
diff --git a/media/video/capture/linux/video_capture_device_chromeos.cc b/media/video/capture/linux/video_capture_device_chromeos.cc
index fd213e0a744103affe2ebb42885f755960764a93..d701077b41305a2399b8afd772d574178f6a4a41 100644
--- a/media/video/capture/linux/video_capture_device_chromeos.cc
+++ b/media/video/capture/linux/video_capture_device_chromeos.cc
@@ -82,7 +82,8 @@ class VideoCaptureDeviceChromeOS::ScreenObserverDelegate
 
   void SendDisplayRotationOnCaptureThread(const gfx::Display& display) {
     DCHECK(capture_task_runner_->BelongsToCurrentThread());
-    capture_device_->SetDisplayRotation(display);
+    if (capture_device_)
+      capture_device_->SetDisplayRotation(display);
   }
 
   VideoCaptureDeviceChromeOS* capture_device_;