Fix a potential segfault in GpuVideoDecoder

media/filters/gpu_video_decoder.cc

Index: media/filters/gpu_video_decoder.cc
diff --git a/media/filters/gpu_video_decoder.cc b/media/filters/gpu_video_decoder.cc
index 5f65eb2ac90664001b590eca9c3472967df98cc3..f52ef5d330a07f56cb80378018de2eeb7a86fca9 100644
--- a/media/filters/gpu_video_decoder.cc
+++ b/media/filters/gpu_video_decoder.cc
@@ -287,6 +287,12 @@ void GpuVideoDecoder::CompleteInitialization(int cdm_id, int surface_id) {
   DCheckGpuVideoAcceleratorFactoriesTaskRunnerIsCurrent();
   DCHECK(!init_cb_.is_null());
 
+  // It's possible for the vda to become null if NotifyError is called.
+  if (!vda_) {
+    base::ResetAndReturn(&init_cb_).Run(false);
+    return;
+  }
+
   VideoDecodeAccelerator::Config vda_config;
   vda_config.profile = config_.profile();
   vda_config.cdm_id = cdm_id;