Re-enable MESA_framebuffer_flip_y extension

BUG=964010

(cherry picked from commit bb06cb374591bb848cb5cae6815a2456c2df911f)

Change-Id: Ie096562c2363e72518c368d546f1d8ef4f92655a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1656451
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Fritz Koenig <frkoenig@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#668629}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1661456
Cr-Commit-Position: refs/branch-heads/3809@{#347}
Cr-Branched-From: d82dec1a818f378c464ba307ddd9c92133eac355-refs/heads/master@{#665002}

diff --git a/gpu/config/gpu_driver_bug_list.json b/gpu/config/gpu_driver_bug_list.json
index 9f264b9..e48371b 100644
--- a/gpu/config/gpu_driver_bug_list.json
+++ b/gpu/config/gpu_driver_bug_list.json

@@ -3276,14 +3276,6 @@
       ]
     },
     {
-      "id": 305,
-      "description": "Disable MESA_framebuffer_flip_y until passing WebGL 2.0 Conformance tests",
-      "cr_bugs": [964010],
-      "disabled_extensions": [
-        "GL_MESA_framebuffer_flip_y"
-      ]
-    },
-    {
       "id": 306,
       "description": "Program binaries don't contain transform feedback varyings on Mali GPUs",
       "cr_bugs": [961950],