Bug 1599529 - Use JSWindowActor message for Picture-in-Picture keyboard shortcut, and enable shortcut for Linux GTK. r=mstriemer

Differential Revision: https://phabricator.services.mozilla.com/D54786

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

browser/base/content/browser-sets.inc

@@ -213,7 +213,7 @@
     <key id="key_toggleReaderMode" keycode="&toggleReaderMode.win.keycode;" command="View:ReaderView" disabled="true"/>
 #endif
 
-#ifdef XP_WIN
+#ifndef XP_MACOSX
     <key id="key_togglePictureInPicture" key="&togglePictureInPicture.key;" command="View:PictureInPicture" modifiers="accel,shift"/>
     <key                                 key="&togglePictureInPicture.key2;" command="View:PictureInPicture" modifiers="accel,shift"/>
 #endif

toolkit/components/pictureinpicture/PictureInPicture.jsm

@@ -149,7 +149,10 @@ var PictureInPicture = {
   onCommand(event) {
     let win = event.target.ownerGlobal;
     let browser = win.gBrowser.selectedBrowser;
-    browser.messageManager.sendAsyncMessage("PictureInPicture:KeyToggle");
+    let actor = browser.browsingContext.currentWindowGlobal.getActor(
+      "PictureInPicture"
+    );
+    actor.sendAsyncMessage("PictureInPicture:KeyToggle");
   },
 
   async focusTabAndClosePip() {