Add Field Trial Testing Configuration for KeepAliveRendererForKeepaliveRequests

Bug: 695939
Change-Id: I39a9e9ce3b030ec233a03912a3b55d25fffa46a4
Reviewed-on: https://chromium-review.googlesource.com/652208
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501209}

testing/variations/fieldtrial_testing_config.json

@@ -1395,6 +1395,25 @@
             ]
         }
     ],
+    "KeepAliveRendererForKeepaliveRequests": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "win"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "KeepAliveRendererForKeepaliveRequests"
+                    ]
+                }
+            ]
+        }
+    ],
     "LazyParseCSS": [
         {
             "platforms": [