Revert following changes for fixing Primetime issue:

- Issue #26 Part 2a: make more EME code conditional. (99118e38e)
- Issue #26 - Part 2b: Stub out GMPDecryptorProxy functions. (d44c61bf6)
- Issue #26 - Part 2c: Remove dependence on gmp/widevine-adapter/* (4c9689f68)
- Issue #1392 - Change --enable-eme to MOZ_ARG_ENABLE_BOOL and remove MOZ_EME_MODULES (832d84d2c)
- [Basilisk] Issue MoonchildProductions/UXP#1392 - Remove usage of MOZ_EME_MODULES (3a165cd)
- Issue #65 - Remove AppConstants from toolkit/mozapps/extensions (758618b60)

dom/html/HTMLMediaElement.cpp

@@ -1871,20 +1871,6 @@ nsresult HTMLMediaElement::LoadResource()
   // Set the media element's CORS mode only when loading a resource
   mCORSMode = AttrValueToCORSMode(GetParsedAttr(nsGkAtoms::crossorigin));
 
-#ifdef MOZ_EME
-  bool isBlob = false;
-  if (mMediaKeys &&
-      Preferences::GetBool("media.eme.mse-only", true) &&
-      // We only want mediaSource URLs, but they are BlobURL, so we have to
-      // check the schema and abort if they are not MediaStream or real Blob.
-      (NS_FAILED(mLoadingSrc->SchemeIs(BLOBURI_SCHEME, &isBlob)) ||
-       !isBlob ||
-       IsMediaStreamURI(mLoadingSrc) ||
-       IsBlobURI(mLoadingSrc))) {
-    return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
-  }
-#endif
-
   HTMLMediaElement* other = LookupMediaElementURITable(mLoadingSrc);
   if (other && other->mDecoder) {
     // Clone it.
@@ -4014,6 +4000,7 @@ nsresult HTMLMediaElement::FinishDecoderSetup(MediaDecoder* aDecoder,
       return NS_ERROR_FAILURE;
     }
   }
+#endif
 
   MediaEventSource<void>* waitingForKeyProducer = mDecoder->WaitingForKeyEvent();
   // Not every decoder will produce waitingForKey events, only add ones that can
@@ -4021,7 +4008,6 @@ nsresult HTMLMediaElement::FinishDecoderSetup(MediaDecoder* aDecoder,
     mWaitingForKeyListener = waitingForKeyProducer->Connect(
       AbstractThread::MainThread(), this, &HTMLMediaElement::CannotDecryptWaitingForKey);
   }
-#endif
 
   if (mChannelLoader) {
     mChannelLoader->Done();
@@ -6490,6 +6476,7 @@ HTMLMediaElement::GetTopLevelPrincipal()
   principal = doc->NodePrincipal();
   return principal.forget();
 }
+#endif //MOZ_EME
 
 void
 HTMLMediaElement::CannotDecryptWaitingForKey()
@@ -6508,7 +6495,6 @@ HTMLMediaElement::CannotDecryptWaitingForKey()
     UpdateReadyStateInternal();
   }
 }
-#endif //MOZ_EME
 
 NS_IMETHODIMP HTMLMediaElement::WindowAudioCaptureChanged(bool aCapture)
 {