Revert "Bug 2053553 Remove unused WebRender debug preferences. r=emilio,layout-reviewers" for causing bustage @ gfxPlatform.cpp

This reverts commit bb40ca9.

Author: Norisz Fay

modules/libpref/init/StaticPrefList.yaml

@@ -8362,6 +8362,11 @@
   value: false
   mirror: always
 
+- name: gfx.webrender.debug.slow-cpu-frame-threshold
+  type: AtomicFloat
+  value: 10.0
+  mirror: always
+
 - name: gfx.webrender.late-scenebuild-threshold
   type: RelaxedAtomicInt32
   value: 4

modules/libpref/init/all.js

@@ -409,13 +409,15 @@ pref("gfx.webrender.debug.texture-cache", false);
 pref("gfx.webrender.debug.texture-cache.clear-evicted", true);
 pref("gfx.webrender.debug.render-targets", false);
 pref("gfx.webrender.debug.gpu-cache", false);
+pref("gfx.webrender.debug.alpha-primitives", false);
 pref("gfx.webrender.debug.profiler", false);
 pref("gfx.webrender.debug.gpu-time-queries", false);
 pref("gfx.webrender.debug.gpu-sample-queries", false);
 pref("gfx.webrender.debug.disable-batching", false);
 pref("gfx.webrender.debug.epochs", false);
 pref("gfx.webrender.debug.echo-driver-messages", false);
 pref("gfx.webrender.debug.show-overdraw", false);
+pref("gfx.webrender.debug.slow-frame-indicator", false);
 pref("gfx.webrender.debug.picture-caching", false);
 pref("gfx.webrender.debug.picture-borders", false);
 pref("gfx.webrender.debug.force-picture-invalidation", false);