🛃 Create field trial testing config for CCT Header.

Bug: 1040143
Change-Id: I30c0988fe53933014805bdec25effa16002baef8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2135759Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Peter Conn <peconn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758761}

testing/variations/fieldtrial_testing_config.json

@@ -1278,6 +1278,25 @@
             ]
         }
     ],
+    "CctClientDataHeader": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "params": {
+                        "expected_version": "300000000",
+                        "header_value": "header value"
+                    },
+                    "enable_features": [
+                        "CCTClientDataHeader"
+                    ]
+                }
+            ]
+        }
+    ],
     "CertDualVerificationTrial": [
         {
             "platforms": [