Add description for new scheduler performance benchmark.

BUG=307841

Review URL: https://codereview.chromium.org/136883004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244550 0039d316-1c4b-4281-b951-d872f2087c98

tools/perf/test-info.json

@@ -180,6 +180,9 @@
       "chrome/src/tools/perf/benchmark/peacekeeper.py"
     ]
   },
+  "scheduler.tough_scheduling_cases":{
+    "description":"This test measures rendering statistics while interacting with pages that have challenging scheduling properties. Mainly affected by changes to the compositor scheduler or the graphics pipeline."
+  },
   "scirra":{
     "description":"The Scirra WebGL performance test measures the number of 2D triangles represented onscreen when the animation reaches the 30 FPS threshold. [Scirra demos](https://www.scirra.com/)",
     "code":[