Add a testing configuration for HTMLParsingYieldTime study.

Corresponds to http://cl/221021676

Bug: 868246
Change-Id: I26f7fe58f07ecfcbe1b540b7c805f575b8b73320
Reviewed-on: https://chromium-review.googlesource.com/c/1198363Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608141}

testing/variations/fieldtrial_testing_config.json

@@ -2160,6 +2160,30 @@
             ]
         }
     ],
+    "HTMLParsingYieldTime": [
+        {
+            "platforms": [
+                "android",
+                "android_webview",
+                "chromeos",
+                "ios",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled_50ms",
+                    "params": {
+                        "limit": "0.05"
+                    },
+                    "enable_features": [
+                        "HTMLParsingYieldTime"
+                    ]
+                }
+            ]
+        }
+    ],
     "HTTPBadPhase3": [
         {
             "platforms": [