Finch: Add config for SqlTempStoreMemory (SQL temporary storage config).

Bug: 875538
Change-Id: Ic0e1f11eb0d0dfcadd6e75ebfad5ffa60d778e2c
Reviewed-on: https://chromium-review.googlesource.com/1183786Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584868}

testing/variations/fieldtrial_testing_config.json

@@ -4109,6 +4109,25 @@
             ]
         }
     ],
+    "SqlTempStoreMemory": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "ios",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "SqlTempStoreMemory"
+                    ]
+                }
+            ]
+        }
+    ],
     "StabilityDebugging": [
         {
             "platforms": [