Added reduced WebGL case from Animometer to tough_webgl_cases.

tools/perf/page_sets/data/tough_webgl_cases.json

 {
-    "description": "Describes the Web Page Replay archives for a page set. Don't edit by hand! Use record_wpr for updating.", 
+    "description": "Describes the Web Page Replay archives for a story set. Don't edit by hand! Use record_wpr for updating.", 
     "archives": {
+        "tough_webgl_cases_004.wpr": [
+            "http://www.khronos.org/registry/webgl/sdk/demos/webkit/ManyPlanetsDeep.html", 
+            "http://www.khronos.org/registry/webgl/sdk/demos/google/san-angeles/index.html", 
+            "http://webglsamples.org/blob/blob.html", 
+            "http://webglsamples.org/dynamic-cubemap/dynamic-cubemap.html", 
+            "http://www.khronos.org/registry/webgl/sdk/demos/google/nvidia-vertex-buffer-object/index.html", 
+            "http://webglsamples.org/aquarium/aquarium.html", 
+            "http://www.khronos.org/registry/webgl/sdk/demos/google/particles/index.html", 
+            "http://kenrussell.github.io/webgl-animometer/Animometer/tests/3d/webgl.html", 
+            "http://www.khronos.org/registry/webgl/sdk/demos/webkit/Earth.html"
+        ], 
         "tough_webgl_cases_000.wpr": [
             "http://montagestudio.com/demos/eco-homes/", 

[aiolos (Not reviewing), 2016/05/11 22:03:03]

Did you get an error message for why these pages failed to re-record? The sites
still seems to be up and running. You should probably file a bug on wpr for
those urls.

[Ken Russell (switch to Gerrit), 2016/05/11 22:11:50]

These two were removed from the page set a while back because they weren't
producing stable numbers. I assume that this is why the JSON file doesn't
contain them any more. Please correct me if I'm misunderstanding.

-            "http://helloracer.com/racer-s/", 
-            "http://www.khronos.org/registry/webgl/sdk/demos/google/nvidia-vertex-buffer-object/index.html", 
-            "http://www.khronos.org/registry/webgl/sdk/demos/google/san-angeles/index.html", 
-            "http://www.khronos.org/registry/webgl/sdk/demos/google/particles/index.html", 
-            "http://www.khronos.org/registry/webgl/sdk/demos/webkit/Earth.html", 
-            "http://www.khronos.org/registry/webgl/sdk/demos/webkit/ManyPlanetsDeep.html", 
-            "http://webglsamples.googlecode.com/hg/aquarium/aquarium.html", 
-            "http://webglsamples.googlecode.com/hg/blob/blob.html", 
-            "http://webglsamples.googlecode.com/hg/dynamic-cubemap/dynamic-cubemap.html"
+            "http://helloracer.com/racer-s/"
         ]
     }
-}
+}