Add testing config for Phase 2 of security indicator experiment

This differs from the initial phase's testing config as the default
behavior is now to show only the lock icon for non-EV HTTPS sites, so
we set the new testing config to "both-to-lock" to set it to the lock
icon for all HTTPS.

Bug: 803138
Change-Id: Ia3a7a4e1b07098e0cfa73d95fa2866fdad8b7343
Reviewed-on: https://chromium-review.googlesource.com/1153565Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Christopher Thompson <cthomp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578812}

testing/variations/fieldtrial_testing_config.json

@@ -3910,7 +3910,7 @@
             ]
         }
     ],
-    "SimplifyHttpsIndicator": [
+    "SimplifyHttpsIndicatorPhase2": [
         {
             "platforms": [
                 "chromeos",
@@ -3920,9 +3920,9 @@
             ],
             "experiments": [
                 {
-                    "name": "EvToSecure",
+                    "name": "BothToLock",
                     "params": {
-                        "treatment": "ev-to-secure"
+                        "treatment": "both-to-lock"
                     },
                     "enable_features": [
                         "SimplifyHttpsIndicator"