Enable MimeHandlerViewInCrossProcessFrame in fieldtrial_testing_config.

Bug: 944162
Change-Id: Ida4c249129686077b15ba9d2c246bcaf8067977e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1603964
Auto-Submit: Łukasz Anforowicz <lukasza@chromium.org>
Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662466}

testing/variations/fieldtrial_testing_config.json

@@ -2942,6 +2942,24 @@
             ]
         }
     ],
+    "MimeHandlerViewInCrossProcessFrame": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "MimeHandlerViewInCrossProcessFrame"
+                    ]
+                }
+            ]
+        }
+    ],
     "MirrorMultilogin": [
         {
             "platforms": [