Fix a crash in AVDA when dereferencing a null task runner

media/gpu/android_video_decode_accelerator.cc

 // Copyright (c) 2013 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 "media/gpu/android_video_decode_accelerator.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 241 matching lines @@
 
     thread_avda_instances_.erase(avda);
     // Post a task to stop the thread through the thread's task runner and back
     // to this thread. This ensures that all pending tasks are run first. If the
     // thread is hung we don't post a task to avoid leaking an unbounded number
     // of tasks on its queue. If the thread is not hung, but appears to be, it
     // will stay alive until next time an AVDA tries to stop it. We're
     // guaranteed to not run StopThreadTask() when the thread is hung because if
     // an AVDA queues tasks after DoNothing(), the StopThreadTask() reply will
     // be canceled by invalidating its weak pointer.
-    if (thread_avda_instances_.empty() &&
+    if (thread_avda_instances_.empty() && construction_thread_.IsRunning() &&
         !hang_detector_.IsThreadLikelyHung()) {
       construction_thread_.task_runner()->PostTaskAndReply(
           FROM_HERE, base::Bind(&base::DoNothing),
           base::Bind(&AVDAManager::StopThreadTask,
                      weak_this_factory_.GetWeakPtr()));
     }
   }
 
   // Request periodic callback of |avda|->DoIOTask(). Does nothing if the
   // instance is already registered and the timer started. The first request
@@ skipping 1507 matching lines @@
 
 bool AndroidVideoDecodeAccelerator::IsMediaCodecSoftwareDecodingForbidden()
     const {
   // Prevent MediaCodec from using its internal software decoders when we have
   // more secure and up to date versions in the renderer process.
   return !config_.is_encrypted && (codec_config_->codec_ == media::kCodecVP8 ||
                                    codec_config_->codec_ == media::kCodecVP9);
 }
 
 }  // namespace media