Add the fieldtrial testing config for ProactiveTabDiscarding.

Bug: 775644, 773382
Change-Id: I8c0426728b31644797e6e641d16ac049ab61a8ce
Reviewed-on: https://chromium-review.googlesource.com/1148950Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578113}

testing/variations/fieldtrial_testing_config.json

@@ -725,27 +725,6 @@
             ]
         }
     ],
-    "BetterMultiTabsLoading": [
-        {
-            "platforms": [
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "PageAlmostIdleSignalEnabled2",
-                    "params": {
-                        "mainThreadTaskLoadLowThreshold": "25"
-                    },
-                    "enable_features": [
-                        "PageAlmostIdle"
-                    ]
-                }
-            ]
-        }
-    ],
     "BlinkSchedulerDedicatedWorkerThrottling": [
         {
             "platforms": [
@@ -3195,6 +3174,32 @@
             ]
         }
     ],
+    "ProactiveTabFreezeAndDiscard": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "FreezeAndDiscardWithUnfreeze",
+                    "params": {
+                        "ShouldPeriodicallyUnfreeze": "true",
+                        "ShouldProactivelyDiscard": "true",
+                        "mainThreadTaskLoadLowThreshold": "25"
+                    },
+                    "enable_features": [
+                        "PageAlmostIdle",
+                        "PageLifecycle",
+                        "ProactiveTabFreezeAndDiscard",
+                        "SiteCharacteristicsDatabase"
+                    ]
+                }
+            ]
+        }
+    ],
     "ProgressBarAnimationAndroid": [
         {
             "platforms": [