Bug 1551570 - Ensure Picture-in-Picture player window is closed before updating internal state. r=JSON_voorhees

Differential Revision: https://phabricator.services.mozilla.com/D31081

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

toolkit/components/pictureinpicture/PictureInPicture.jsm

@@ -52,25 +52,28 @@ var PictureInPicture = {
     }
   },
 
-  focusTabAndClosePip() {
+  async focusTabAndClosePip() {
     let gBrowser = this.browser.ownerGlobal.gBrowser;
     let tab = gBrowser.getTabForBrowser(this.browser);
     gBrowser.selectedTab = tab;
-    this.unload();
-    this.closePipWindow();
+    await this.closePipWindow();
   },
 
   /**
    * Find and close any pre-existing Picture in Picture windows.
    */
-  closePipWindow() {
+  async closePipWindow() {
     // This uses an enumerator, but there really should only be one of
     // these things.
     for (let win of Services.wm.getEnumerator(WINDOW_TYPE)) {
       if (win.closed) {
         continue;
       }
+      let closedPromise = new Promise(resolve => {
+        win.addEventListener("unload", resolve, {once: true});
+      });
       win.close();
+      await closedPromise;
     }
   },
 
@@ -95,9 +98,11 @@ var PictureInPicture = {
    *   the player component inside it has finished loading.
    */
   async handlePictureInPictureRequest(browser, videoData) {
-    this.browser = browser;
+    // If there's a pre-existing PiP window, close it first.
+    await this.closePipWindow();
+
     let parentWin = browser.ownerGlobal;
-    this.closePipWindow();
+    this.browser = browser;
     let win = await this.openPipWindow(parentWin, videoData);
     let controls = win.document.getElementById("controls");
     this.weakPipControls = Cu.getWeakReference(controls);

toolkit/components/pictureinpicture/content/player.js

@@ -41,7 +41,7 @@ async function setupPlayer(originatingBrowser, videoData) {
     window.close();
   });
 
-  browser.addEventListener("unload", () => {
+  window.addEventListener("unload", () => {
     PictureInPicture.unload();
   });