Defines NoScriptPreviews fieldtrial for test config

This is needed to land a Beta channel finch config for this study.

Bug: 776847
Change-Id: Ied77a7ad58e6d1f7d75ea1502eac982bdec834fd
Reviewed-on: https://chromium-review.googlesource.com/959611Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Doug Arnett <dougarnett@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542942}

testing/variations/fieldtrial_testing_config.json

@@ -2715,6 +2715,22 @@
             ]
         }
     ],
+    "PreviewsNoScript": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "NoScriptWithWhiteList2",
+                    "enable_features": [
+                        "NoScriptPreviews",
+                        "OptimizationHints"
+                    ]
+                }
+            ]
+        }
+    ],
     "PrintPdfAsImage": [
         {
             "platforms": [