Don't include MediaKeySystemAccess without EME.

This also removes checks for EME content in documents.
This removes practical use of EME by no longer having a keying system. (no-op)
tag #26

dom/base/nsDocument.cpp

@@ -4340,6 +4340,7 @@ nsDocument::SetScopeObject(nsIGlobalObject* aGlobal)
   }
 }
 
+#ifdef MOZ_EME
 static void
 CheckIfContainsEMEContent(nsISupports* aSupports, void* aContainsEME)
 {
@@ -4363,6 +4364,7 @@ nsDocument::ContainsEMEContent()
                              static_cast<void*>(&containsEME));
   return containsEME;
 }
+#endif // MOZ_EME
 
 static void
 CheckIfContainsMSEContent(nsISupports* aSupports, void* aContainsMSE)
@@ -8390,11 +8392,13 @@ nsDocument::CanSavePresentation(nsIRequest *aNewRequest)
   }
 #endif // MOZ_WEBRTC
 
+#ifdef MOZ_EME
   // Don't save presentations for documents containing EME content, so that
   // CDMs reliably shutdown upon user navigation.
   if (ContainsEMEContent()) {
     return false;
   }
+#endif
 
   // Don't save presentations for documents containing MSE content, to
   // reduce memory usage.