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/media/platforms/PDMFactory.h

@@ -11,9 +11,7 @@
 #include "mozilla/Function.h"
 #include "mozilla/StaticMutex.h"
 
-#ifdef MOZ_EME
 class CDMProxy;
-#endif
 
 namespace mozilla {
 
@@ -40,14 +38,12 @@ public:
   bool Supports(const TrackInfo& aTrackInfo,
                 DecoderDoctorDiagnostics* aDiagnostics) const;
 
-#ifdef MOZ_EME
   // Creates a PlatformDecoderModule that uses a CDMProxy to decrypt or
   // decrypt-and-decode EME encrypted content. If the CDM only decrypts and
   // does not decode, we create a PDM and use that to create MediaDataDecoders
   // that we use on on aTaskQueue to decode the decrypted stream.
   // This is called on the decode task queue.
   void SetCDMProxy(CDMProxy* aProxy);
-#endif
 
   static constexpr int kYUV400 = 0;
   static constexpr int kYUV420 = 1;