Bug 1530471 - remove --disable-skia-gpu since Skia GPU is no longer used r=glandium

Differential Revision: https://phabricator.services.mozilla.com/D21050

--HG--
extra : moz-landing-system : lando

toolkit/moz.configure

@@ -806,21 +806,6 @@ def skia_android(skia, target):
 
 set_define('SK_BUILD_FOR_ANDROID_NDK', skia_android)
 
-option('--disable-skia-gpu', help='Disable use of Skia-GPU')
-
-@depends('--disable-skia-gpu', skia)
-def skia_gpu(value, skia):
-    if value.origin == 'default':
-        if not skia:
-            return None
-    elif value and not skia:
-        die('Cannot enable Skia-GPU without enabling Skia')
-    if skia and value:
-        return True
-
-set_config('MOZ_ENABLE_SKIA_GPU', skia_gpu)
-set_define('USE_SKIA_GPU', skia_gpu)
-
 option('--enable-skia-pdf', help='Enable Skia PDF')
 
 @depends('--enable-skia-pdf', skia, target, milestone)