Bug 1208371 - Add an interface DecoderPrincipalChangeObserver to HTMLMediaElement. r=roc

MozReview-Commit-ID: DwDHDE7SLxY

--HG--
extra : rebase_source : 73f74260d8b62bb4838ab5a5c4b2153a251c5d95

dom/html/HTMLMediaElement.cpp

@@ -4191,6 +4191,21 @@ void HTMLMediaElement::NotifyDecoderPrincipalChanged()
     ms->mStream->SetCORSMode(mCORSMode);
     ms->mStream->CombineWithPrincipal(principal);
   }
+
+  for (DecoderPrincipalChangeObserver* observer :
+         mDecoderPrincipalChangeObservers) {
+    observer->NotifyDecoderPrincipalChanged();
+  }
+}
+
+void HTMLMediaElement::AddDecoderPrincipalChangeObserver(DecoderPrincipalChangeObserver* aObserver)
+{
+  mDecoderPrincipalChangeObservers.AppendElement(aObserver);
+}
+
+bool HTMLMediaElement::RemoveDecoderPrincipalChangeObserver(DecoderPrincipalChangeObserver* aObserver)
+{
+  return mDecoderPrincipalChangeObservers.RemoveElement(aObserver);
 }
 
 void HTMLMediaElement::UpdateMediaSize(const nsIntSize& aSize)

dom/html/HTMLMediaElement.h

@@ -265,7 +265,30 @@ public:
   already_AddRefed<nsIPrincipal> GetCurrentPrincipal();
 
   // called to notify that the principal of the decoder's media resource has changed.
-  virtual void NotifyDecoderPrincipalChanged() final override;
+  void NotifyDecoderPrincipalChanged() final override;
+
+  // An interface for observing principal changes on the media elements
+  // MediaDecoder.
+  class DecoderPrincipalChangeObserver
+  {
+  public:
+    virtual void NotifyDecoderPrincipalChanged() = 0;
+  };
+
+  /**
+   * Add a DecoderPrincipalChangeObserver to this media element.
+   *
+   * Ownership of the DecoderPrincipalChangeObserver remains with the caller,
+   * and it's the caller's responsibility to remove the observer before it dies.
+   */
+  void AddDecoderPrincipalChangeObserver(DecoderPrincipalChangeObserver* aObserver);
+
+  /**
+   * Remove an added DecoderPrincipalChangeObserver from this media element.
+   *
+   * Returns true if it was successfully removed.
+   */
+  bool RemoveDecoderPrincipalChangeObserver(DecoderPrincipalChangeObserver* aObserver);
 
   // Update the visual size of the media. Called from the decoder on the
   // main thread when/if the size changes.
@@ -1111,6 +1134,10 @@ protected:
   // At most one of mDecoder and mSrcStream can be non-null.
   RefPtr<MediaDecoder> mDecoder;
 
+  // Observers listening to changes to the mDecoder principal.
+  // Used by streams captured from this element.
+  nsTArray<DecoderPrincipalChangeObserver*> mDecoderPrincipalChangeObservers;
+
   // State-watching manager.
   WatchManager<HTMLMediaElement> mWatchManager;