Bug 1509047 - Part 4: Add support for PermissionPromptPrototype.onBeforeShow() cancelling a prompt r=johannh

Depends on D12864

Differential Revision: https://phabricator.services.mozilla.com/D12865

--HG--
extra : moz-landing-system : lando

browser/modules/PermissionUI.jsm

@@ -253,8 +253,12 @@ var PermissionPromptPrototype = {
    * be called just before. Subclasses may want to override this
    * in order to, for example, bump a counter Telemetry probe for
    * how often a particular permission request is seen.
+   *
+   * If this returns false, it cancels the process of showing the prompt.  In
+   * that case, it is the responsibility of the onBeforeShow() implementation
+   * to ensure that allow() or cancel() are called on the object appropriately.
    */
-  onBeforeShow() {},
+  onBeforeShow() { return true; },
 
   /**
    * If the prompt was shown to the user, this callback will be called just
@@ -440,14 +444,15 @@ var PermissionPromptPrototype = {
       return false;
     };
 
-    this.onBeforeShow();
-    chromeWin.PopupNotifications.show(this.browser,
-                                      this.notificationID,
-                                      this.message,
-                                      this.anchorID,
-                                      mainAction,
-                                      secondaryActions,
-                                      options);
+    if (this.onBeforeShow() !== false) {
+      chromeWin.PopupNotifications.show(this.browser,
+                                        this.notificationID,
+                                        this.message,
+                                        this.anchorID,
+                                        mainAction,
+                                        secondaryActions,
+                                        options);
+    }
   },
 };
 
@@ -590,6 +595,7 @@ GeolocationPermissionPrompt.prototype = {
     let secHistogram = Services.telemetry.getHistogramById("SECURITY_UI");
     const SHOW_REQUEST = Ci.nsISecurityUITelemetry.WARNING_GEOLOCATION_REQUEST;
     secHistogram.add(SHOW_REQUEST);
+    return true;
   },
 };
 
@@ -826,9 +832,6 @@ MIDIPermissionPrompt.prototype = {
         action: Ci.nsIPermissionManager.DENY_ACTION,
     }];
   },
-
-  onBeforeShow() {
-  },
 };
 
 PermissionUI.MIDIPermissionPrompt = MIDIPermissionPrompt;
@@ -911,6 +914,7 @@ AutoplayPermissionPrompt.prototype = {
     };
     this.browser.addEventListener(
       "DOMAudioPlaybackStarted", this.handlePlaybackStart);
+    return true;
   },
 };
 

browser/modules/test/browser/browser_PermissionUI.js

@@ -294,6 +294,7 @@ add_task(async function test_on_before_show() {
       promptActions: [mainAction],
       onBeforeShow() {
         beforeShown = true;
+        return true;
       },
     };
 
@@ -353,6 +354,7 @@ add_task(async function test_no_request() {
       promptActions: [mainAction, secondaryAction],
       onBeforeShow() {
         beforeShown = true;
+        return true;
       },
     };