Declare the new TranslateCompactUI experiments for fieldtrial testing.

This CL adds some new "TranslateCompactUI" experiments to the
fieldtrial for testing different values of auto-never theshold in the
compact UI on Android.

Bug: 720184
Change-Id: I3360d5724b212ca7aba62b484803e402d54da260
Reviewed-on: https://chromium-review.googlesource.com/623016
Commit-Queue: Marti Wong <martiw@chromium.org>
Reviewed-by: Alexei Svitkine (very slow) <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#496539}

testing/variations/fieldtrial_testing_config.json

@@ -3137,7 +3137,10 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled",
+                    "name": "NeverThresholdEquals7",
+                    "params": {
+                        "translate_auto_never_threshold": "7"
+                    },
                     "enable_features": [
                         "TranslateCompactUI"
                     ]