Add LowerJavaScriptPriorityWhenForceDeferred to field trial

Bug: 978490
Change-Id: I0169f66399a9f02dcca8cce5e0e6aaefde1d67a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869448
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Auto-Submit: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707535}

testing/variations/fieldtrial_testing_config.json

@@ -3269,8 +3269,8 @@
             ],
             "experiments": [
                 {
-                    "name": "Control_20190905",
-                    "disable_features": [
+                    "name": "Enabled_20190905",
+                    "enable_features": [
                         "LowerJavaScriptPriorityWhenForceDeferred"
                     ]
                 }