Bug 1877416 - handle reentrancy when showing infobars via EncryptedMediaParent.receiveMessage r=reusable-components-reviewers,tgiles

`notificationBox.appendNotification` is now async, so in cases where we were receiving multiple "cdm-not-installed" messages in quick succession it was possible that the notification from the prior call hadn't actully been appended yet. This made it so that calls to `notificationBox.getNotificationWithValue` wouldn't return anything, and we would show the same message multiple times. This patch adds code to track which notification related messages are being handled to avoid re-appending the same notification.

Differential Revision: https://phabricator.services.mozilla.com/D200030

browser/actors/EncryptedMediaParent.sys.mjs

@@ -59,7 +59,10 @@ export class EncryptedMediaParent extends JSWindowActorParent {
     ]);
   }
 
-  receiveMessage(aMessage) {
+  async receiveMessage(aMessage) {
+    if (!this.handledMessages) {
+      this.handledMessages = new Set();
+    }
     // The top level browsing context's embedding element should be a xul browser element.
     let browser = this.browsingContext.top.embedderElement;
 
@@ -76,6 +79,9 @@ export class EncryptedMediaParent extends JSWindowActorParent {
       return;
     }
     let { status, keySystem } = parsedData;
+    if (this.handledMessages.has(status)) {
+      return;
+    }
 
     // First, see if we need to do updates. We don't need to do anything for
     // hidden keysystems:
@@ -108,6 +114,7 @@ export class EncryptedMediaParent extends JSWindowActorParent {
 
       case "api-disabled":
       case "cdm-disabled":
+        this.handledMessages.add(status);
         notificationId = "drmContentDisabled";
         buttonCallback = () => {
           this.ensureEMEEnabled(browser, keySystem);
@@ -119,6 +126,7 @@ export class EncryptedMediaParent extends JSWindowActorParent {
         break;
 
       case "cdm-not-installed":
+        this.handledMessages.add(status);
         notificationId = "drmContentCDMInstalling";
         notificationMessage = this.getMessageWithBrandName(notificationId);
         break;
@@ -143,6 +151,7 @@ export class EncryptedMediaParent extends JSWindowActorParent {
 
     let notificationBox = browser.getTabBrowser().getNotificationBox(browser);
     if (notificationBox.getNotificationWithValue(notificationId)) {
+      this.handledMessages.delete(status);
       return;
     }
 
@@ -162,7 +171,7 @@ export class EncryptedMediaParent extends JSWindowActorParent {
     }
 
     let iconURL = "chrome://browser/skin/drm-icon.svg";
-    notificationBox.appendNotification(
+    await notificationBox.appendNotification(
       notificationId,
       {
         label: notificationMessage,
@@ -171,6 +180,7 @@ export class EncryptedMediaParent extends JSWindowActorParent {
       },
       buttons
     );
+    this.handledMessages.delete(status);
   }
 
   async showPopupNotificationForSuccess(aBrowser) {

browser/base/content/test/plugins/browser_enable_DRM_prompt.js

@@ -244,3 +244,55 @@ add_task(async function test_drm_prompt_shows_for_cross_origin_iframe() {
     );
   });
 });
+
+add_task(async function test_drm_prompt_only_shows_one_notification() {
+  await BrowserTestUtils.withNewTab(TEST_URL, async function (browser) {
+    // Turn off EME and Widevine CDM.
+    Services.prefs.setBoolPref("media.eme.enabled", false);
+    Services.prefs.setBoolPref("media.gmp-widevinecdm.enabled", false);
+    let notificationShownPromise = BrowserTestUtils.waitForNotificationBar(
+      gBrowser,
+      browser,
+      "drmContentDisabled"
+    );
+
+    // Send three EME requests to ensure only one instance of the
+    // "Enable DRM" notification appears in the chrome
+    for (let i = 0; i < 3; i++) {
+      await SpecialPowers.spawn(browser, [], async function () {
+        try {
+          let config = [
+            {
+              initDataTypes: ["webm"],
+              videoCapabilities: [{ contentType: 'video/webm; codecs="vp9"' }],
+            },
+          ];
+          await content.navigator.requestMediaKeySystemAccess(
+            "com.widevine.alpha",
+            config
+          );
+        } catch (ex) {
+          return { rejected: true };
+        }
+        return { rejected: false };
+      });
+    }
+
+    // Verify the UI prompt showed.
+    let box = gBrowser.getNotificationBox(browser);
+    await notificationShownPromise;
+    let notification = box.currentNotification;
+
+    ok(notification, "Notification should be visible");
+    is(
+      notification.getAttribute("value"),
+      "drmContentDisabled",
+      "Should be showing the right notification"
+    );
+    is(
+      box.allNotifications.length,
+      1,
+      "There should only be one notification shown"
+    );
+  });
+});