MD Settings: Allow deleting read-only content setting exceptions.

chrome/browser/resources/settings/site_settings/site_list.js

Index: chrome/browser/resources/settings/site_settings/site_list.js
diff --git a/chrome/browser/resources/settings/site_settings/site_list.js b/chrome/browser/resources/settings/site_settings/site_list.js
index 7765e36d08cbcab3489a2b7a9aeb1f3f86231df6..2e491c77f6fb51e488302bf534a0c153609aa8cb 100644
--- a/chrome/browser/resources/settings/site_settings/site_list.js
+++ b/chrome/browser/resources/settings/site_settings/site_list.js
@@ -494,6 +494,16 @@ Polymer({
    * @param {!{model: !{item: !SiteException}}} e
    * @private
    */
+  onResetButtonTap_: function(e) {
+    // Trigger same logic as opening the menu and choosing the Reset item.
+    this.actionMenuSite_ = e.model.item;
+    this.onResetTap_();

[dschuyler, 2017/03/22 18:33:08]

It looks like only
this.onActionMenuActivate_(settings.PermissionValues.DEFAULT);
is necessary?
I'm not clear on why we'd call this.closeActionMenu_(). I suppose it's probably
harmless and would be fine if it were really hard to avoid that code path, but
it looks easy to avoid that path (though maybe I'm missing something?).

[tommycli, 2017/03/22 21:05:37]

Done.

+  },
+
+  /**
+   * @param {!{model: !{item: !SiteException}}} e
+   * @private
+   */
   onShowActionMenuTap_: function(e) {
     this.actionMenuSite_ = e.model.item;
     /** @type {!CrActionMenuElement} */ (