Update RendererSideResourceScheduler testing config

Bug: 785770, 794073
Change-Id: I0e4ee3a24ee3b480fe88022fc489f231ad779990
Reviewed-on: https://chromium-review.googlesource.com/821335Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523396}

testing/variations/fieldtrial_testing_config.json

@@ -2907,6 +2907,25 @@
             ]
         }
     ],
+    "RendererSideResourceScheduler": [
+        {
+            "platforms": [
+                "win",
+                "mac",
+                "linux",
+                "chromeos",
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "RendererSideResourceScheduler"
+                    ]
+                }
+            ]
+        }
+    ],
     "ReportCertificateErrors": [
         {
             "platforms": [