Add V8Ignition field-trial.

testing/variations/fieldtrial_testing_config.json

 {
     "AlternateComponentUrls": [
         {
             "platforms": [
                 "android",
                 "chromeos",
                 "ios",
                 "linux",
                 "mac",
                 "win"
@@ skipping 2841 matching lines @@
                 },
                 {
                     "name": "normal"
                 },
                 {
                     "name": "aggressive"
                 }
             ]
         }
     ],
+    "V8Ignition": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "win"
+            ],
+            "experiments": [
+                {
+                    "name": "Control3"
+                },
+                {
+                    "name": "Future"

[rkaplow, 2017/03/13 17:10:06]

this only can test one, so I would add jsut Future here (assuming that's the
main feature being tested)

[rmcilroy, 2017/03/14 09:57:49]

Done.

+                }
+            ]
+        }
+    ],
     "ViewsSimplifiedFullscreenUI": [
         {
             "platforms": [
                 "mac"
             ],
             "experiments": [
                 {
                     "name": "Enabled",
                     "enable_features": [
                         "ViewsSimplifiedFullscreenUI"
@@ skipping 139 matching lines @@
                 {
                     "name": "Enabled",
                     "enable_features": [
                         "use-new-media-cache"
                     ]
                 }
             ]
         }
     ]
 }