MD Settings: implement support for extension-controlled startup URLs

chrome/browser/resources/settings/controls/controlled_radio_button.js

Index: chrome/browser/resources/settings/controls/controlled_radio_button.js
diff --git a/chrome/browser/resources/settings/controls/controlled_radio_button.js b/chrome/browser/resources/settings/controls/controlled_radio_button.js
index cf697206d0d34ec9b661ceb0f252fcac6ccd2ee7..516efb0db75cac11d387de3ed87c46ae0b068b2d 100644
--- a/chrome/browser/resources/settings/controls/controlled_radio_button.js
+++ b/chrome/browser/resources/settings/controls/controlled_radio_button.js
@@ -30,7 +30,7 @@ Polymer({
    * @private
    */
   computeControlled_: function() {
-    return this.isPrefPolicyControlled(assert(this.pref));
+    return this.pref.enforcement == chrome.settingsPrivate.Enforcement.ENFORCED;

[dpapad, 2016/11/18 23:46:28]

This is subtle. What is the difference between |pref.enforcement| and
|pref.policyEnforcement| which the  isPrefPolicyControlled refers to? Should we
just update |isPrefPolicyControlled| to look for both?

[Dan Beam, 2016/11/18 23:51:04]

the code you're looking at is outdated, there's only enforcement now

also, isPrefPolicyControlled() does exactly what it says: returns true if the
pref is POLICY controlled.  we need the radio group to be disabled if it's
POLICY controlled OR EXTENSION controlled.  they're not the same.

[dpapad, 2016/11/19 00:20:15]

Ok. I am slightly confused, so I am going to ask qustions to get a better
understanding.

Q1: CrPolicyPrefBehavior, is about POLICY controlled things only, and
PrefControlBehavior has nothing to do with prefs that are "controlled by"
(policy, extension, etc). Is my understanding accurate? If yes, isn't it
confusing if it has nothing to do with "controlled by" things?

Q2: Is this element using any of the CrPolicyPrefBehavior methods anymore? Or
can that behavior be removed?

[Dan Beam, 2016/11/19 00:50:05]

yes
yes
it's "control" as in a button or input.  we should rename it, along with
SettingsBooleanControlBehaviorImpl.
removed

   },
 
   /**