Add BrowserScheduler to fieldtrial testing config.

Only DetachTimeFg16x is added because it is the most
different variation from control, while other variations
test values in between.


Bug: 847501
Change-Id: I12da837873f86345e36cfb9577a7a803015baa40
Reviewed-on: https://chromium-review.googlesource.com/1249805Reviewed-by: Robert Kaplow (sloooow) <rkaplow@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595520}

testing/variations/fieldtrial_testing_config.json

@@ -1032,6 +1032,21 @@
             ]
         }
     ],
+    "BrowserScheduler": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux"
+            ],
+            "experiments": [
+                {
+                    "name": "DetachTimeFg16x"
+                }
+            ]
+        }
+    ],
     "BundledConnectionHelp": [
         {
             "platforms": [