Don't build EME-specific subroutines without EME.

- Checks for restricted or encrypted content
- Dispatching 'encrypted' events
- Dispatching 'key needed' events
- HTML Media Element media keys system
- EME telemetry
- HTML Media Element EME API

This is the main bulk for #26, isolating EME-specific code.

dom/html/HTMLMediaElement.h

@@ -20,7 +20,9 @@
 #include "mozilla/dom/TextTrackManager.h"
 #include "mozilla/WeakPtr.h"
 #include "MediaDecoder.h"
+#ifdef MOZ_EME
 #include "mozilla/dom/MediaKeys.h"
+#endif
 #include "mozilla/StateWatching.h"
 #include "nsGkAtoms.h"
 #include "PrincipalChangeObserver.h"
@@ -630,6 +632,7 @@ public:
 
   // XPCOM MozPreservesPitch() is OK
 
+#ifdef MOZ_EME
   MediaKeys* GetMediaKeys() const;
 
   already_AddRefed<Promise> SetMediaKeys(MediaKeys* mediaKeys,
@@ -651,6 +654,7 @@ public:
   already_AddRefed<nsIPrincipal> GetTopLevelPrincipal();
 
   bool ContainsRestrictedContent();
+#endif // MOZ_EME
 
   void CannotDecryptWaitingForKey();
 
@@ -1198,7 +1202,9 @@ protected:
    */
   void HiddenVideoStop();
 
+#ifdef MOZ_EME
   void ReportEMETelemetry();
+#endif
 
   void ReportTelemetry();
 
@@ -1471,8 +1477,10 @@ protected:
   // Timer used to simulate video-suspend.
   nsCOMPtr<nsITimer> mVideoDecodeSuspendTimer;
 
+#ifdef MOZ_EME
   // Encrypted Media Extension media keys.
   RefPtr<MediaKeys> mMediaKeys;
+#endif
 
   // Stores the time at the start of the current 'played' range.
   double mCurrentPlayRangeStart;
@@ -1627,8 +1635,10 @@ protected:
   // Listens for waitingForKey events from the owned decoder.
   MediaEventListener mWaitingForKeyListener;
 
+#ifdef MOZ_EME
   // Init Data that needs to be sent in 'encrypted' events in MetadataLoaded().
   EncryptionInfo mPendingEncryptedInitData;
+#endif
 
   // True if the media's channel's download has been suspended.
   Watchable<bool> mDownloadSuspendedByCache;