Bug 1618691 - Simplify RootActor::listTabs response r=ochameau

Depends on D65693

Differential Revision: https://phabricator.services.mozilla.com/D70174

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

devtools/client/fronts/root.js

@@ -194,18 +194,6 @@ class RootFront extends FrontClassWithSpec(rootSpec) {
     return this.getProcess(0);
   }
 
-  /**
-   * Override default listTabs request in order to return a list of
-   * BrowsingContextTargetFronts while updating their selected state.
-   *
-   * Backward compatibility: favicons is only useful for FF75 or older.
-   * It can be removed when Firefox 76 hits the release channel.
-   */
-  async listTabs({ favicons } = {}) {
-    const { tabs } = await super.listTabs({ favicons });
-    return tabs;
-  }
-
   /**
    * Fetch the target actor for the currently selected tab, or for a specific
    * tab given as first parameter.

devtools/server/actors/root.js

@@ -249,8 +249,7 @@ exports.RootActor = protocol.ActorClassWithSpec(rootSpec, {
 
   /**
    * Gets the "root" form, which lists all the global actors that affect the entire
-   * browser.  This can replace usages of `listTabs` that only wanted the global actors
-   * and didn't actually care about tabs.
+   * browser.
    */
   getRoot: function() {
     // Create global actors
@@ -271,12 +270,6 @@ exports.RootActor = protocol.ActorClassWithSpec(rootSpec, {
   /**
    * Handles the listTabs request. The actors will survive until at least
    * the next listTabs request.
-   *
-   * ⚠ WARNING ⚠ This can be a very expensive operation, especially if there are many
-   * open tabs.  It will cause us to visit every tab, load a frame script, start a
-   * devtools server, and read some data.  With lazy tab support (bug 906076), this
-   * would trigger any lazy tabs to be loaded, greatly increasing resource usage.  Avoid
-   * this method whenever possible.
    */
   listTabs: async function() {
     const tabList = this._parameters.tabList;
@@ -302,9 +295,6 @@ exports.RootActor = protocol.ActorClassWithSpec(rootSpec, {
       newActorPool.manage(tabDescriptorActor);
     }
 
-    // Start with the root reply, which includes the global actors for the whole browser.
-    const reply = this.getRoot();
-
     // Drop the old actorID -> actor map. Actors that still mattered were added to the
     // new map; others will go away.
     if (this._tabDescriptorActorPool) {
@@ -312,12 +302,7 @@ exports.RootActor = protocol.ActorClassWithSpec(rootSpec, {
     }
     this._tabDescriptorActorPool = newActorPool;
 
-    // We'll extend the reply here to also mention all the tabs.
-    Object.assign(reply, {
-      tabs: [...this._tabDescriptorActorPool.poolChildren()],
-    });
-
-    return reply;
+    return tabDescriptorActors;
   },
 
   getTab: async function({ outerWindowID, tabId }) {

devtools/shared/specs/root.js

@@ -20,9 +20,6 @@ types.addDictType("root.listServiceWorkerRegistrations", {
 types.addDictType("root.listRemoteFrames", {
   frames: "array:frameDescriptor",
 });
-types.addDictType("root.listTabs", {
-  tabs: "array:tabDescriptor",
-});
 types.addPolymorphicType("root.browsingContextDescriptor", [
   "frameDescriptor",
   "processDescriptor",
@@ -43,7 +40,9 @@ const rootSpecPrototype = {
         // The argument can be dropped when FF76 hits the release channel.
         favicons: Option(0, "boolean"),
       },
-      response: RetVal("root.listTabs"),
+      response: {
+        tabs: RetVal("array:tabDescriptor"),
+      },
     },
 
     getTab: {