Bug 1145101: Part3. Ensure PDM is shutdown after decoder. r=cpearce

A MediaDataDecoder object can't be used once the PDM that created it is
shutdown.
We ensure that if the PDM is in use by the SharedDecoderManager we do not
shut it down.

dom/media/fmp4/MP4Reader.cpp

@@ -205,7 +205,10 @@ MP4Reader::Shutdown()
   mQueuedVideoSample = nullptr;
 
   if (mPlatform) {
-    mPlatform->Shutdown();
+    if (!mSharedDecoderManager ||
+        !mSharedDecoderManager->IsPDMInUse(mPlatform)) {
+      mPlatform->Shutdown();
+    }
     mPlatform = nullptr;
   }
 

dom/media/fmp4/SharedDecoderManager.cpp

@@ -83,8 +83,10 @@ SharedDecoderManager::CreateVideoDecoder(
     mDecoder = aPDM->CreateVideoDecoder(
       aConfig, aLayersBackend, aImageContainer, mTaskQueue, mCallback);
     if (!mDecoder) {
+      mPDM = nullptr;
       return nullptr;
     }
+    mPDM = aPDM;
     nsresult rv = mDecoder->Init();
     NS_ENSURE_SUCCESS(rv, nullptr);
   }
@@ -103,8 +105,10 @@ SharedDecoderManager::Recreate(PlatformDecoderModule* aPDM,
   mDecoder->Shutdown();
   mDecoder = aPDM->CreateVideoDecoder(aConfig, aLayersBackend, aImageContainer, mTaskQueue, mCallback);
   if (!mDecoder) {
+    mPDM = nullptr;
     return false;
   }
+  mPDM = aPDM;
   nsresult rv = mDecoder->Init();
   return rv == NS_OK;
 }
@@ -168,6 +172,10 @@ SharedDecoderManager::Shutdown()
     mDecoder->Shutdown();
     mDecoder = nullptr;
   }
+  if (mPDM) {
+    mPDM->Shutdown();
+    mPDM = nullptr;
+  }
   if (mTaskQueue) {
     mTaskQueue->BeginShutdown();
     mTaskQueue->AwaitShutdownAndIdle();
@@ -175,6 +183,12 @@ SharedDecoderManager::Shutdown()
   }
 }
 
+bool
+SharedDecoderManager::IsPDMInUse(const mozilla::PlatformDecoderModule* aPDM) const
+{
+  return aPDM == mPDM;
+}
+
 SharedDecoderProxy::SharedDecoderProxy(
   SharedDecoderManager* aManager, MediaDataDecoderCallback* aCallback)
   : mManager(aManager), mCallback(aCallback)

dom/media/fmp4/SharedDecoderManager.h

@@ -36,6 +36,7 @@ public:
   void SetIdle(MediaDataDecoder* aProxy);
   void ReleaseMediaResources();
   void Shutdown();
+  bool IsPDMInUse(const PlatformDecoderModule* aPDM) const;
 
   friend class SharedDecoderProxy;
   friend class SharedDecoderCallback;
@@ -49,6 +50,7 @@ private:
   virtual ~SharedDecoderManager();
   void DrainComplete();
 
+  nsRefPtr<PlatformDecoderModule> mPDM;
   nsRefPtr<MediaDataDecoder> mDecoder;
   nsRefPtr<FlushableMediaTaskQueue> mTaskQueue;
   SharedDecoderProxy* mActiveProxy;