Remove references to page_cycler_v2.tough_layout_cases (deleted benchmark)

Bug: 767546
Change-Id: Ia829774573ba0c329a52055e34be77dfa6a82d52
Reviewed-on: https://chromium-review.googlesource.com/677644Reviewed-by: Helen Li <xunjieli@chromium.org>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#503579}

tools/perf/core/desktop_benchmark_avg_times.json

@@ -9,7 +9,7 @@
     "blink_perf.dom": 98.51104682236321,
     "blink_perf.events": 66.05652102455497,
     "blink_perf.layout": 453.38422619201697,
-    "blink_perf.owp_storage": 30.0, 
+    "blink_perf.owp_storage": 30.0,
     "blink_perf.paint": 51.07198746293505,
     "blink_perf.parser": 400.27208882935196,
     "blink_perf.shadow_dom": 81.56559749378646,
@@ -56,7 +56,6 @@
     "page_cycler_v2.intl_ja_zh": 2381.6099734405675,
     "page_cycler_v2.intl_ko_th_vi": 1651.235684189815,
     "page_cycler_v2.top_10_mobile": 671.6237025374458,
-    "page_cycler_v2.tough_layout_cases": 1047.1903459546722,
     "page_cycler_v2.typical_25": 2253.314608139926,
     "page_cycler_v2_site_isolation.basic_oopif": 513.9117965158755,
     "power.steady_state": 596.0703444047408,

tools/perf/page_sets/data/tough_layout_cases.json

-{
-    "archives": {
-        "http://amarchoti.blogspot.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://bookish.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://chinaapache.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://indoritel.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://mydiyclub.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://natunkantha.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://oilevent.com": {
-            "DEFAULT": "tough_layout_cases_001.wpr"
-        },
-        "http://picarisimo.es": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://www.mossiella.com": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        },
-        "http://www.muzoboss.ru": {
-            "DEFAULT": "tough_layout_cases_000.wpr"
-        }
-    },
-    "description": "Describes the Web Page Replay archives for a story set. Don't edit by hand! Use record_wpr for updating.",
-    "platform_specific": true
-}
\ No newline at end of file

tools/perf/page_sets/data/tough_layout_cases_000.wpr.sha1

-3c4f0c5a3d32a61b6e8f5d76ab476e39fef977aa
\ No newline at end of file