--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -246,16 +246,38 @@ public:
   explicit WaitForCDMState(Master* aPtr) : StateObject(aPtr) {}
 
   State GetState() const override
   {
     return DECODER_STATE_WAIT_FOR_CDM;
   }
 };
 
+class MediaDecoderStateMachine::DormantState
+  : public MediaDecoderStateMachine::StateObject
+{
+public:
+  explicit DormantState(Master* aPtr) : StateObject(aPtr) {}
+
+  void Enter() override
+  {
+    mMaster->DiscardSeekTaskIfExist();
+    if (mMaster->IsPlaying()) {
+      mMaster->StopPlayback();
+    }
+    mMaster->Reset();
+    mMaster->mReader->ReleaseResources();
+  }
+
+  State GetState() const override
+  {
+    return DECODER_STATE_DORMANT;
+  }
+};
+
 #define INIT_WATCHABLE(name, val) \
   name(val, "MediaDecoderStateMachine::" #name)
 #define INIT_MIRROR(name, val) \
   name(mTaskQueue, val, "MediaDecoderStateMachine::" #name " (Mirror)")
 #define INIT_CANONICAL(name, val) \
   name(mTaskQueue, val, "MediaDecoderStateMachine::" #name " (Canonical)")
 
 MediaDecoderStateMachine::MediaDecoderStateMachine(MediaDecoder* aDecoder,
@@ -1116,16 +1138,19 @@ MediaDecoderStateMachine::SetState(State
 
   switch (mState) {
     case DECODER_STATE_DECODING_METADATA:
       mStateObj = MakeUnique<DecodeMetadataState>(this);
       break;
     case DECODER_STATE_WAIT_FOR_CDM:
       mStateObj = MakeUnique<WaitForCDMState>(this);
       break;
+    case DECODER_STATE_DORMANT:
+      mStateObj = MakeUnique<DormantState>(this);
+      break;
     default:
       mStateObj = nullptr;
       break;
   }
 
   EnterState();
 }
 
@@ -1159,24 +1184,16 @@ MediaDecoderStateMachine::EnterState()
 
   if (mStateObj) {
     MOZ_ASSERT(mState == mStateObj->GetState());
     mStateObj->Enter();
     return;
   }
 
   switch (mState) {
-    case DECODER_STATE_DORMANT:
-      DiscardSeekTaskIfExist();
-      if (IsPlaying()) {
-        StopPlayback();
-      }
-      Reset();
-      mReader->ReleaseResources();
-      break;
     case DECODER_STATE_DECODING_FIRSTFRAME:
       DecodeFirstFrame();
       break;
     case DECODER_STATE_DECODING:
       StartDecoding();
       break;
     case DECODER_STATE_BUFFERING:
       StartBuffering();