Bug 1383628. P5 - move CanClone() from MediaResource to BaseMediaResource. r=gerald

1. we move clone related methods to BaseMediaResource which is the only cloneable sub-class of MediaResource.
2. add CanClone() to ChannelMediaDecoder to reduce the dependency on MediaResource for HTMLMediaElement.
   MediaResource should be internal details to MediaDecoder.

MozReview-Commit-ID: Hl2nAiuyTO0

--HG--
extra : rebase_source : 43dd9ee33ef2ef2e9093eb6b264dc174379d61d2
extra : source : 978ded48a90f2c407c4545486243acabf492736a

dom/html/HTMLMediaElement.cpp

@@ -3744,9 +3744,11 @@ HTMLMediaElement::LookupMediaElementURITable(nsIURI* aURI)
     // Ditto for anything else that could cause us to send different headers.
     if (NS_SUCCEEDED(elem->NodePrincipal()->Equals(NodePrincipal(), &equal)) && equal &&
         elem->mCORSMode == mCORSMode) {
-      NS_ASSERTION(elem->mDecoder && elem->mDecoder->GetResource(), "Decoder gone");
-      MediaResource* resource = elem->mDecoder->GetResource();
-      if (resource->CanClone()) {
+      // See SetupDecoder() below. We only add a element to the table when
+      // mDecoder is a ChannelMediaDecoder.
+      auto decoder = static_cast<ChannelMediaDecoder*>(elem->mDecoder.get());
+      NS_ASSERTION(decoder, "Decoder gone");
+      if (decoder->CanClone()) {
         return elem;
       }
     }

dom/media/ChannelMediaDecoder.cpp

@@ -155,6 +155,13 @@ ChannelMediaDecoder::ChannelMediaDecoder(MediaDecoderInit& aInit)
   mResourceCallback->Connect(this);
 }
 
+bool
+ChannelMediaDecoder::CanClone()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  return mResource && mResource->CanClone();
+}
+
 already_AddRefed<ChannelMediaDecoder>
 ChannelMediaDecoder::Clone(MediaDecoderInit& aInit)
 {

dom/media/ChannelMediaDecoder.h

@@ -66,6 +66,8 @@ public:
 
   void Shutdown() override;
 
+  bool CanClone();
+
   // Create a new decoder of the same type as this one.
   already_AddRefed<ChannelMediaDecoder> Clone(MediaDecoderInit& aInit);
 

dom/media/MediaResource.h

@@ -174,12 +174,6 @@ public:
   virtual void Resume() = 0;
   // Get the current principal for the channel
   virtual already_AddRefed<nsIPrincipal> GetCurrentPrincipal() = 0;
-  // If this returns false, then we shouldn't try to clone this MediaResource
-  // because its underlying resources are not suitable for reuse (e.g.
-  // because the underlying connection has been lost, or this resource
-  // just can't be safely cloned). If this returns true, CloneData could
-  // still fail. If this returns false, CloneData should not be called.
-  virtual bool CanClone() { return false; }
 
   // These methods are called off the main thread.
   // The mode is initially MODE_PLAYBACK.
@@ -331,6 +325,13 @@ public:
     nsIChannel* aChannel,
     bool aIsPrivateBrowsing);
 
+  // If this returns false, then we shouldn't try to clone this MediaResource
+  // because its underlying resources are not suitable for reuse (e.g.
+  // because the underlying connection has been lost, or this resource
+  // just can't be safely cloned). If this returns true, CloneData could
+  // still fail. If this returns false, CloneData should not be called.
+  virtual bool CanClone() { return false; }
+
   // Create a new stream of the same type that refers to the same URI
   // with a new channel. Any cached data associated with the original
   // stream should be accessible in the new stream too.