[iOS] Add breadcrumbs feature to fieldtrial_testing_config

Bug: 1082892
Change-Id: I10a20600fcea65a32e32a2a656f1e3a2f3a01f4e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2226779
Auto-Submit: Mike Dougherty <michaeldo@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774804}

testing/variations/fieldtrial_testing_config.json

@@ -2830,6 +2830,21 @@
             ]
         }
     ],
+    "IOSCrashReportBreadcrumbs": [
+        {
+            "platforms": [
+                "ios"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "LogBreadcrumbs"
+                    ]
+                }
+            ]
+        }
+    ],
     "IOSEmbedderBlockRestoreUrl": [
         {
             "platforms": [