Make extensions developer mode adhere to policy

chrome/test/data/policy/policy_test_cases.json

Index: chrome/test/data/policy/policy_test_cases.json
diff --git a/chrome/test/data/policy/policy_test_cases.json b/chrome/test/data/policy/policy_test_cases.json
index 7ac8f033e592a1a9af344ef758040e24906e4565..63b3be9ad4b965bea202ac24c55ca75c0d98e919 100644
--- a/chrome/test/data/policy/policy_test_cases.json
+++ b/chrome/test/data/policy/policy_test_cases.json
@@ -14,6 +14,7 @@
         "check_for_recommended": "Should the preference be tested when a recommended value is set for the policy? Defaults to |true| if not specified.",
         "note": "When |can_be_recommended| is |false|, the policy is never set to a recommended value so |check_for_recommended| has no effect.",
         "note": "The following entries should be specified if controlled setting indicators exist for |pref| in the settings UI.",
+        "indicator_test_url": "The URL to navigate to in order to test the indicators. Defaults to |chrome://settings-frame/| if not specified.",
         "indicator_test_setup_js": "Any JavaScript that should be executed before testing the indicators. This should be specified only if an explicit user action must be simulated (e.g. clicking a button).",
         "indicator_selector": "A CSS selector that locates all controlled setting indicators for |pref|. This is appended to the selector 'span.controlled-setting-indicator' and if not specified, defaults to '[pref=(the value of |pref|)', e.g. '[pref=homepage]'.",
         "note": "Any number of test cases may be specified in the following array.",
@@ -845,7 +846,13 @@
     "os": ["win", "linux", "mac", "chromeos"],
     "test_policy": { "DeveloperToolsDisabled": true },
     "pref_mappings": [
-      { "pref": "devtools.disabled" }
+      { "pref": "devtools.disabled",
+        "indicator_test_url": "chrome://extensions-frame/",
+        "indicator_selector": "#dev-toggle-disabled-by-policy-indicator",
+        "indicator_tests": [
+          { "policy": { "DeveloperToolsDisabled": true } }
+        ]
+      }
     ]
   },