Bug 1854298 - Implement PrintingEnabled policy r=emilio,mkaply,Gijs,fluent-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D188792

browser/base/content/browser.js

@@ -586,6 +586,16 @@ XPCOMUtils.defineLazyPreferenceGetter(
   }
 );
 
+XPCOMUtils.defineLazyPreferenceGetter(
+  this,
+  "gPrintEnabled",
+  "print.enabled",
+  false,
+  (aPref, aOldVal, aNewVal) => {
+    updatePrintCommands(aNewVal);
+  }
+);
+
 XPCOMUtils.defineLazyPreferenceGetter(
   this,
   "gScreenshotsComponentEnabled",
@@ -847,6 +857,19 @@ function UpdateBackForwardCommands(aWebNavigation) {
   }
 }
 
+function updatePrintCommands(enabled) {
+  var printCommand = document.getElementById("cmd_print");
+  var printPreviewCommand = document.getElementById("cmd_printPreviewToggle");
+
+  if (enabled) {
+    printCommand.removeAttribute("disabled");
+    printPreviewCommand.removeAttribute("disabled");
+  } else {
+    printCommand.setAttribute("disabled", "true");
+    printPreviewCommand.setAttribute("disabled", "true");
+  }
+}
+
 /**
  * Click-and-Hold implementation for the Back and Forward buttons
  * XXXmano: should this live in toolbarbutton.js?
@@ -1643,6 +1666,8 @@ var gBrowserInit = {
 
     updateFxaToolbarMenu(gFxaToolbarEnabled, true);
 
+    updatePrintCommands(gPrintEnabled);
+
     gUnifiedExtensions.init();
 
     // Setting the focus will cause a style flush, it's preferable to call anything