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)

old-configure.in

@@ -2901,12 +2901,25 @@ dnl ========================================================
 dnl = EME support
 dnl ========================================================
 
-MOZ_ARG_ENABLE_BOOL(eme,
-[  --enable-eme           Enable support for Encrypted Media Extensions  ],
-    MOZ_EME=1,
-    MOZ_EME=)
+MOZ_ARG_ENABLE_STRING(eme,
+[  --enable-eme[=widevine]  Enable support for Encrypted Media Extensions  ],
+    MOZ_EME_ARGS=$enableval)
 
+if test "$MOZ_EME_ARGS"; then
+    if test "$MOZ_EME_ARGS" = "no"; then
+        dnl EME explicitly disabled with --disable-eme
+        MOZ_EME=
+    elif test "$MOZ_EME_ARGS" = "yes"; then
+        dnl EME explicitly enabled with --enable-eme
+        MOZ_EME=1
+    else
+        dnl EME explicitly enabled with --enable-eme=<args>
+        MOZ_EME=1
+        MOZ_EME_MODULES=`echo $MOZ_EME_ARGS | sed -e 's/,/ /g'`
+    fi
+fi
 
+AC_SUBST_SET(MOZ_EME_MODULES)
 if test -n "$MOZ_EME"; then
     if test -z "$MOZ_FMP4"; then
         AC_MSG_ERROR([Encrypted Media Extension support requires Fragmented MP4 support])
@@ -2914,8 +2927,6 @@ if test -n "$MOZ_EME"; then
     AC_DEFINE(MOZ_EME)
 fi
 
-AC_SUBST(MOZ_EME)
-
 MOZ_LIBVPX_CFLAGS=
 MOZ_LIBVPX_LIBS=
 
@@ -5287,6 +5298,7 @@ AC_SUBST(MOZ_VORBIS)
 AC_SUBST(MOZ_TREMOR)
 AC_SUBST(MOZ_FFVPX)
 AC_SUBST_LIST(FFVPX_ASFLAGS)
+AC_SUBST(MOZ_EME)
 AC_SUBST(MOZ_VPX_ERROR_CONCEALMENT)
 AC_SUBST(VPX_USE_YASM)
 AC_SUBST_LIST(VPX_ASFLAGS)