MD Settings: Allow editing startup URLs when "recommended" policy is present.

chrome/browser/resources/settings/on_startup_page/startup_urls_page.html

Index: chrome/browser/resources/settings/on_startup_page/startup_urls_page.html
diff --git a/chrome/browser/resources/settings/on_startup_page/startup_urls_page.html b/chrome/browser/resources/settings/on_startup_page/startup_urls_page.html
index 155ded00997fe08d986b55a1f4ec13e3cc07a5f7..2c915fc68626f6aded78c5a452972e37ae822ca2 100644
--- a/chrome/browser/resources/settings/on_startup_page/startup_urls_page.html
+++ b/chrome/browser/resources/settings/on_startup_page/startup_urls_page.html
@@ -37,13 +37,14 @@
             <settings-startup-url-entry model="[[item]]"
                 tabindex$="[[tabIndex]]" iron-list-tab-index="[[tabIndex]]"
                 last-focused="{{lastFocused_}}"
-                editable="[[!prefs.session.startup_urls.controlledBy]]">
+                editable="[[shouldAllowUrlsEdit_(
+                    prefs.session.startup_urls.enforcement)]]">

[dpapad, 2017/06/23 22:51:04]

Is |enforcement| always set, even when this pref is controlled by an extension?
The test at
https://cs.chromium.org/chromium/src/chrome/test/data/webui/settings/startup_...
suggests so, but want to double check to ensure we are not regressing the
controlled by extension case. 

If this LG, I'll start working on a test (and possibly send as a separate CL).

[stevenjb, 2017/06/23 23:13:15]

This is the only place that I am aware of that we set CONTROLLED_BY_EXTENSION,
and enforcement is always set to ENFORCED:

https://cs.chromium.org/chromium/src/chrome/browser/extensions/api/settings_p...

             </settings-startup-url-entry>
           </template>
         </iron-list>
       </div>
-      <template is="dom-if" if="[[!prefs.session.startup_urls.controlledBy]]"
-          restamp>
+      <template is="dom-if" if="[[shouldAllowUrlsEdit_(
+          prefs.session.startup_urls.enforcement)]]" restamp>

[stevenjb, 2017/06/23 23:13:15]

I forget, is this guaranteed to get stamped if enforcement is not defined?

[dpapad, 2017/06/23 23:42:30]

Yes. I had the same question, so I made a minimal example at
https://jsfiddle.net/sf3rtyny/. Basically as long as |prefs| is defined, the
function will be called, even if subproperties are undefined.

FWIW, this is not documented so explicitly in Polymer's doc, I only reached this
conclusion by experimentation.

Polymer's docs at
https://www.polymer-project.org/1.0/docs/devguide/data-binding#annotated-comp...
say
"As with observers and computed properties, the computing function is not called
until all dependent properties are defined (!=undefined)."

         <div class="list-item" id="addPage">
           <a is="action-link" class="list-button" on-tap="onAddPageTap_">
             $i18n{onStartupAddNewPage}