Android PiP: add field trial testing entry for finch config.

Bug: 1021681
Change-Id: I551f94a2d195a8235a2c5292dbae67ccae5089b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1904494Reviewed-by: Nik Bhagat <nikunjb@chromium.org>
Commit-Queue: Jazz Xu <jazzhsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715334}

testing/variations/fieldtrial_testing_config.json

@@ -519,6 +519,21 @@
             ]
         }
     ],
+    "AndroidPictureInPictureAPI": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Disabled",
+                    "disable_features": [
+                        "PictureInPictureAPI"
+                    ]
+                }
+            ]
+        }
+    ],
     "AndroidSpellChecker": [
         {
             "platforms": [