Bug 1300956. Part 1 - Add declarations of the state objects of MDSM. Also implement DecodeMetadataState. r=kaku

MozReview-Commit-ID: BRyi409rmn5

--HG--
extra : rebase_source : 369b2654a77c76aa5654680f8cce763e67205fc2

dom/media/MediaDecoderStateMachine.cpp

@@ -204,6 +204,41 @@ SuspendBackgroundVideoDelay()
     MediaPrefs::MDSMSuspendBackgroundVideoDelay());
 }
 
+class MediaDecoderStateMachine::StateObject
+{
+public:
+  virtual ~StateObject() {}
+  virtual void Enter() {}; // Entry action.
+  virtual void Exit() {};  // Exit action.
+  virtual void Step() {}   // Perform a 'cycle' of this state object.
+  virtual State GetState() const = 0;
+
+protected:
+  using Master = MediaDecoderStateMachine;
+  explicit StateObject(Master* aPtr) : mMaster(aPtr) {}
+
+  // Take a raw pointer in order not to change the life cycle of MDSM.
+  // It is guaranteed to be valid by MDSM.
+  Master* mMaster;
+};
+
+class MediaDecoderStateMachine::DecodeMetadataState
+  : public MediaDecoderStateMachine::StateObject
+{
+public:
+  explicit DecodeMetadataState(Master* aPtr) : StateObject(aPtr) {}
+
+  void Enter() override
+  {
+    mMaster->ReadMetadata();
+  }
+
+  State GetState() const override
+  {
+    return DECODER_STATE_DECODING_METADATA;
+  }
+};
+
 #define INIT_WATCHABLE(name, val) \
   name(val, "MediaDecoderStateMachine::" #name)
 #define INIT_MIRROR(name, val) \
@@ -223,6 +258,7 @@ MediaDecoderStateMachine::MediaDecoderStateMachine(MediaDecoder* aDecoder,
   mDispatchedStateMachine(false),
   mDelayedScheduler(mTaskQueue),
   INIT_WATCHABLE(mState, DECODER_STATE_DECODING_METADATA),
+  mStateObj(new DecodeMetadataState(this)),
   mCurrentFrameID(0),
   INIT_WATCHABLE(mObservedDuration, TimeUnit()),
   mFragmentEndTime(-1),
@@ -1065,6 +1101,16 @@ MediaDecoderStateMachine::SetState(State aState)
 
   ExitState();
   mState = aState;
+
+  switch (mState) {
+    case DECODER_STATE_DECODING_METADATA:
+      mStateObj = MakeUnique<DecodeMetadataState>(this);
+      break;
+    default:
+      mStateObj = nullptr;
+      break;
+  }
+
   EnterState();
 }
 
@@ -1072,6 +1118,13 @@ void
 MediaDecoderStateMachine::ExitState()
 {
   MOZ_ASSERT(OnTaskQueue());
+
+  if (mStateObj) {
+    MOZ_ASSERT(mState == mStateObj->GetState());
+    mStateObj->Exit();
+    return;
+  }
+
   switch (mState) {
     case DECODER_STATE_COMPLETED:
       mSentPlaybackEndedEvent = false;
@@ -1088,10 +1141,14 @@ void
 MediaDecoderStateMachine::EnterState()
 {
   MOZ_ASSERT(OnTaskQueue());
+
+  if (mStateObj) {
+    MOZ_ASSERT(mState == mStateObj->GetState());
+    mStateObj->Enter();
+    return;
+  }
+
   switch (mState) {
-    case DECODER_STATE_DECODING_METADATA:
-      ReadMetadata();
-      break;
     case DECODER_STATE_DORMANT:
       DiscardSeekTaskIfExist();
       if (IsPlaying()) {
@@ -2263,6 +2320,11 @@ MediaDecoderStateMachine::RunStateMachine()
   mDelayedScheduler.Reset(); // Must happen on state machine task queue.
   mDispatchedStateMachine = false;
 
+  if (mStateObj) {
+    mStateObj->Step();
+    return;
+  }
+
   switch (mState) {
     case DECODER_STATE_DECODING:
       StepDecoding();

dom/media/MediaDecoderStateMachine.h

@@ -251,6 +251,17 @@ public:
   size_t SizeOfAudioQueue() const;
 
 private:
+  class StateObject;
+  class DecodeMetadataState;
+  class WaitForCDMState;
+  class DormantState;
+  class DecodingFirstFrameState;
+  class DecodingState;
+  class SeekingState;
+  class BufferingState;
+  class CompletedState;
+  class ShutdownState;
+
   static const char* ToStateStr(State aState);
   const char* ToStateStr();
 
@@ -603,6 +614,8 @@ private:
   // Accessed on state machine, audio, main, and AV thread.
   Watchable<State> mState;
 
+  UniquePtr<StateObject> mStateObj;
+
   // Time that buffering started. Used for buffering timeout and only
   // accessed on the state machine thread. This is null while we're not
   // buffering.