Remove GStreamer code from the build system

dom/media/moz.build

@@ -29,9 +29,6 @@ if CONFIG['MOZ_WAVE']:
 if CONFIG['MOZ_WEBM']:
     DIRS += ['webm']
 
-if CONFIG['MOZ_GSTREAMER']:
-    DIRS += ['gstreamer']
-
 if CONFIG['MOZ_DIRECTSHOW']:
     DIRS += ['directshow']
 

layout/build/moz.build

@@ -116,9 +116,6 @@ if CONFIG['MOZ_WEBSPEECH']:
         '/dom/media/webspeech/synth',
     ]
 
-if CONFIG['MOZ_GSTREAMER']:
-    CXXFLAGS += CONFIG['GSTREAMER_CFLAGS']
-
 if CONFIG['MOZ_SECUREELEMENT']:
     LOCAL_INCLUDES += [
         '/dom/secureelement',

toolkit/library/moz.build

@@ -356,9 +356,6 @@ if CONFIG['OS_ARCH'] == 'WINNT':
 if CONFIG['MOZ_ENABLE_QT']:
     OS_LIBS += CONFIG['XEXT_LIBS']
 
-if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'cocoa' and CONFIG['MOZ_GSTREAMER']:
-    OS_LIBS += CONFIG['GSTREAMER_LIBS']
-
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'windows':
     OS_LIBS += [
         'usp10',