Adds TranslateSubFrames config to fieldtrials testing config

Bug: 1063520
Change-Id: I8463fd5a1aad85a42e9700faba5bcef98af64502
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2224975Reviewed-by: Megan Jablonski <megjablon@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Doug Arnett <dougarnett@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773878}

testing/variations/fieldtrial_testing_config.json

@@ -6333,6 +6333,22 @@
             ]
         }
     ],
+    "TranslateSubFramesStudy": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "TranslateSubFrames"
+                }
+            ]
+        }
+    ],
     "TriggeredResetFieldTrial": [
         {
             "platforms": [