[iOS Policy] Add ChromeVariations policy for iOS.

Bug: 1092180
Change-Id: Ib274cb26a85aa9ebc9de34793338c67b935b5cec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2248135Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: sebsg <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779886}

components/policy/resources/policy_templates.json

@@ -12204,6 +12204,7 @@
         },
       ],
       'supported_on': ['chrome.*:83-'],
+      'future_on': ['ios'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,

ios/chrome/browser/policy/BUILD.gn

@@ -30,6 +30,8 @@ source_set("policy") {
     "//components/safe_browsing/core/common:safe_browsing_prefs",
     "//components/search_engines",
     "//components/translate/core/browser:translate_pref_names",
+    "//components/variations",
+    "//components/variations/service",
     "//ios/chrome/browser",
     "//ios/chrome/browser:pref_names",
     "//ios/chrome/browser/browser_state",

ios/chrome/browser/policy/configuration_policy_handler_list_factory.mm

@@ -22,6 +22,8 @@
 #include "components/safe_browsing/core/common/safe_browsing_prefs.h"
 #include "components/search_engines/default_search_policy_handler.h"
 #include "components/translate/core/browser/translate_pref_names.h"
+#include "components/variations/pref_names.h"
+#include "components/variations/service/variations_service.h"
 #include "ios/chrome/browser/policy/policy_features.h"
 #include "ios/chrome/browser/pref_names.h"
 
@@ -38,6 +40,9 @@ namespace {
 // that directly map to a single preference.
 // clang-format off
 const PolicyToPreferenceMapEntry kSimplePolicyMap[] = {
+  { policy::key::kChromeVariations,
+    variations::prefs::kVariationsRestrictionsByPolicy,
+    base::Value::Type::INTEGER },
   { policy::key::kEditBookmarksEnabled,
     bookmarks::prefs::kEditBookmarksEnabled,
     base::Value::Type::BOOLEAN },

ios/chrome/test/data/policy/policy_test_cases.json

@@ -46,6 +46,18 @@
     ]
   },
 
+ "ChromeVariations": {
+    "os": [ "ios" ],
+    "policy_pref_mapping_test": [
+      {
+        "policies": {
+          "ChromeVariations": 1
+        },
+        "prefs": { "variations_restrictions_by_policy": { "local_state": true } }
+      }
+    ]
+  },
+
   "DefaultPopupsSetting": {
     "os": [ "ios" ],
     "note": "TODO(crbug.com/106682): Flag this with can_be_recommended",