diff --git a/browser/base/content/webext-panels.js b/browser/base/content/webext-panels.js
index 722d5ac57d17..7e4afdd85a71 100644
--- a/browser/base/content/webext-panels.js
+++ b/browser/base/content/webext-panels.js
@@ -64,8 +64,6 @@ function getBrowser(panel) {
E10SUtils.EXTENSION_REMOTE_TYPE
)
);
- browser.setAttribute("maychangeremoteness", "true");
-
readyPromise = promiseEvent(browser, "XULFrameLoaderCreated");
} else {
readyPromise = Promise.resolve();
diff --git a/browser/components/extensions/ExtensionPopups.jsm b/browser/components/extensions/ExtensionPopups.jsm
index 235bed013ca0..1514e75b7287 100644
--- a/browser/components/extensions/ExtensionPopups.jsm
+++ b/browser/components/extensions/ExtensionPopups.jsm
@@ -321,7 +321,6 @@ class BasePopup {
if (this.extension.remote) {
browser.setAttribute("remote", "true");
browser.setAttribute("remoteType", this.extension.remoteType);
- browser.setAttribute("maychangeremoteness", "true");
}
// We only need flex sizing for the sake of the slide-in sub-views of the
diff --git a/browser/components/extensions/test/browser/browser.ini b/browser/components/extensions/test/browser/browser.ini
index 4a5300bdf775..3a5340c0e234 100644
--- a/browser/components/extensions/test/browser/browser.ini
+++ b/browser/components/extensions/test/browser/browser.ini
@@ -144,7 +144,6 @@ skip-if = (verify && (os == 'linux' || os == 'mac'))
[browser_ext_menus_visible.js]
[browser_ext_menus_viewType.js]
[browser_ext_mousewheel_zoom.js]
-[browser_ext_nontab_process_switch.js]
[browser_ext_omnibox.js]
[browser_ext_openPanel.js]
skip-if = (verify && !debug && (os == 'linux' || os == 'mac'))
diff --git a/browser/components/extensions/test/browser/browser_ext_nontab_process_switch.js b/browser/components/extensions/test/browser/browser_ext_nontab_process_switch.js
deleted file mode 100644
index a39d2514ae27..000000000000
--- a/browser/components/extensions/test/browser/browser_ext_nontab_process_switch.js
+++ /dev/null
@@ -1,79 +0,0 @@
-"use strict";
-
-add_task(async function process_switch_in_sidebars_popups() {
- let extension = ExtensionTestUtils.loadExtension({
- useAddonManager: "temporary", // To automatically show sidebar on load.
- manifest: {
- content_scripts: [
- {
- matches: ["http://example.com/*"],
- js: ["cs.js"],
- },
- ],
- sidebar_action: {
- default_panel: "page.html?sidebar",
- },
- browser_action: {
- default_popup: "page.html?popup",
- },
- },
- files: {
- "page.html": ``,
- async "page.js"() {
- browser.test.sendMessage("extension_page", {
- place: location.search,
- pid: await SpecialPowers.spawnChrome([], () => {
- return windowGlobalParent.osPid;
- }),
- });
- if (!location.search.endsWith("_back")) {
- window.location.href = "http://example.com/" + location.search;
- }
- },
-
- async "cs.js"() {
- browser.test.sendMessage("content_script", {
- url: location.href,
- pid: await this.wrappedJSObject.SpecialPowers.spawnChrome([], () => {
- return windowGlobalParent.osPid;
- }),
- });
- if (location.search === "?popup") {
- window.location.href =
- browser.runtime.getURL("page.html") + "?popup_back";
- }
- },
- },
- });
-
- await extension.startup();
- let sidebar = await extension.awaitMessage("extension_page");
- is(sidebar.place, "?sidebar", "Message from the extension sidebar");
-
- let cs1 = await extension.awaitMessage("content_script");
- is(cs1.url, "http://example.com/?sidebar", "CS on example.com in sidebar");
- isnot(sidebar.pid, cs1.pid, "Navigating to example.com changed process");
-
- await clickBrowserAction(extension);
- let popup = await extension.awaitMessage("extension_page");
- is(popup.place, "?popup", "Message from the extension popup");
-
- let cs2 = await extension.awaitMessage("content_script");
- is(cs2.url, "http://example.com/?popup", "CS on example.com in popup");
- isnot(popup.pid, cs2.pid, "Navigating to example.com changed process");
-
- let popup2 = await extension.awaitMessage("extension_page");
- is(popup2.place, "?popup_back", "Back at extension page in popup");
- is(popup.pid, popup2.pid, "Same process as original popup page");
-
- is(sidebar.pid, popup.pid, "Sidebar and popup pages from the same process");
-
- // Before Fission, there's no guarantee that two (independent) pages
- // from the same domain will end up in the same process.
- if (Services.appinfo.fissionAutostart) {
- is(cs1.pid, cs2.pid, "Both example.com CSs from the same process");
- }
-
- await closeBrowserAction(extension);
- await extension.unload();
-});