Add fieldtrial testing config for SameSiteByDefaultCookies experiments

Bug: 1002052
Change-Id: I3dec0caf2b98b4b89124688386dba23d4f408ee4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890534Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711373}

testing/variations/fieldtrial_testing_config.json

@@ -5391,6 +5391,57 @@
             ]
         }
     ],
+    "SameSiteByDefaultCookies_AndroidAw": [
+        {
+            "platforms": [
+                "android",
+                "android_webview"
+            ],
+            "experiments": [
+                {
+                    "name": "LaxByDefaultAndNoneRequiresSecure",
+                    "enable_features": [
+                        "CookiesWithoutSameSiteMustBeSecure",
+                        "SameSiteByDefaultCookies"
+                    ]
+                }
+            ]
+        }
+    ],
+    "SameSiteByDefaultCookies_Linux": [
+        {
+            "platforms": [
+                "linux"
+            ],
+            "experiments": [
+                {
+                    "name": "LaxByDefaultAndNoneRequiresSecure",
+                    "enable_features": [
+                        "CookiesWithoutSameSiteMustBeSecure",
+                        "SameSiteByDefaultCookies"
+                    ]
+                }
+            ]
+        }
+    ],
+    "SameSiteByDefaultCookies_WinMacCros": [
+        {
+            "platforms": [
+                "chromeos",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "LaxByDefaultAndNoneRequiresSecure",
+                    "enable_features": [
+                        "CookiesWithoutSameSiteMustBeSecure",
+                        "SameSiteByDefaultCookies"
+                    ]
+                }
+            ]
+        }
+    ],
     "SameSiteCookieMessages": [
         {
             "platforms": [