Enable SkiaGL by default on OpenGL compositing platforms

diff --git modules/libpref/init/all.js modules/libpref/init/all.js
index 93e56b00a961..61a2174c3384 100644
--- modules/libpref/init/all.js
+++ modules/libpref/init/all.js
@@ -882,15 +882,9 @@ pref("gfx.font_rendering.opentype_svg.enabled", true);
 pref("gfx.canvas.azure.backends", "direct2d1.1,skia,cairo");
 pref("gfx.content.azure.backends", "direct2d1.1,skia,cairo");
 #else
-#ifdef XP_MACOSX
 pref("gfx.content.azure.backends", "skia");
 pref("gfx.canvas.azure.backends", "skia");
-// Accelerated cg canvas where available (10.7+)
 pref("gfx.canvas.azure.accelerated", true);
-#else
-pref("gfx.canvas.azure.backends", "skia");
-pref("gfx.content.azure.backends", "skia");
-#endif
 #endif
 
 pref("gfx.canvas.skiagl.dynamic-cache", true);