Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

11 files changed, 1032 insertions, 0 deletions

diff --git a/dom/events/test/clipboard/browser.ini b/dom/events/test/clipboard/browser.ini
new file mode 100644
index 0000000000..eb452c1443
--- /dev/null
+++ b/dom/events/test/clipboard/browser.ini
@@ -0,0 +1,21 @@
+[DEFAULT]
+support-files =
+  head.js
+  !/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js
+  !/gfx/layers/apz/test/mochitest/apz_test_utils.js
+
+[browser_navigator_clipboard_readText.js]
+support-files =
+  simple_navigator_clipboard_readText.html
+[browser_navigator_clipboard_read.js]
+support-files =
+  simple_navigator_clipboard_read.html
+[browser_navigator_clipboard_touch.js]
+support-files =
+  simple_navigator_clipboard_readText.html
+[browser_navigator_clipboard_clickjacking.js]
+skip-if =
+  os == "win" # The popupmenus dismiss when access keys for disabled items are pressed on windows
+  os == "mac" && verify
+support-files =
+  simple_navigator_clipboard_keydown.html
diff --git a/dom/events/test/clipboard/browser_navigator_clipboard_clickjacking.js b/dom/events/test/clipboard/browser_navigator_clipboard_clickjacking.js
new file mode 100644
index 0000000000..cd3e97f274
--- /dev/null
+++ b/dom/events/test/clipboard/browser_navigator_clipboard_clickjacking.js
@@ -0,0 +1,69 @@
+/* -*- Mode: JavaScript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const kBaseUrlForContent = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "https://example.com"
+);
+
+const kContentFileName = "simple_navigator_clipboard_keydown.html";
+
+const kContentFileUrl = kBaseUrlForContent + kContentFileName;
+
+const kApzTestNativeEventUtilsUrl =
+  "chrome://mochitests/content/browser/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js";
+
+Services.scriptloader.loadSubScript(kApzTestNativeEventUtilsUrl, this);
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.events.asyncClipboard.readText", true]],
+  });
+});
+
+add_task(async function test_paste_button_clickjacking() {
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+
+    // synthesize key to trigger readText() to bring up paste popup.
+    EventUtils.synthesizeKey("p", {}, window);
+    await waitForPasteMenuPopupEvent("shown");
+
+    const pastePopup = document.getElementById(kPasteMenuPopupId);
+    const pasteButton = document.getElementById(kPasteMenuItemId);
+    ok(
+      pasteButton.disabled,
+      "Paste button should be shown with disabled by default"
+    );
+
+    let accesskey = pasteButton.getAttribute("accesskey");
+    let delay = Services.prefs.getIntPref("security.dialog_enable_delay") * 3;
+    while (delay > 0) {
+      // There's no other way to allow some time to pass and ensure we're
+      // genuinely testing that these keypresses postpone the enabling of
+      // the paste button, so disable this check for this line:
+      // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+      await new Promise(r => setTimeout(r, 100));
+      ok(pasteButton.disabled, "Paste button should still be disabled");
+      EventUtils.synthesizeKey(accesskey, {}, window);
+      is(pastePopup.state, "open", "Paste popup should still be opened");
+      delay = delay - 100;
+    }
+
+    await BrowserTestUtils.waitForMutationCondition(
+      pasteButton,
+      { attributeFilter: ["disabled"] },
+      () => !pasteButton.disabled,
+      "Wait for paste button enabled"
+    );
+
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    EventUtils.synthesizeKey(accesskey, {}, window);
+    await pasteButtonIsHidden;
+  });
+});
diff --git a/dom/events/test/clipboard/browser_navigator_clipboard_read.js b/dom/events/test/clipboard/browser_navigator_clipboard_read.js
new file mode 100644
index 0000000000..5b3af1d116
--- /dev/null
+++ b/dom/events/test/clipboard/browser_navigator_clipboard_read.js
@@ -0,0 +1,198 @@
+/* -*- Mode: JavaScript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const kBaseUrlForContent = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "https://example.com"
+);
+
+const kContentFileName = "simple_navigator_clipboard_read.html";
+
+const kContentFileUrl = kBaseUrlForContent + kContentFileName;
+
+const kApzTestNativeEventUtilsUrl =
+  "chrome://mochitests/content/browser/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js";
+
+Services.scriptloader.loadSubScript(kApzTestNativeEventUtilsUrl, this);
+
+// @param aBrowser browser object of the content tab.
+// @param aMultipleReadTextCalls if false, exactly one call is made, two
+//                               otherwise.
+function promiseClickContentToTriggerClipboardRead(
+  aBrowser,
+  aMultipleReadTextCalls
+) {
+  return promiseClickContentElement(
+    aBrowser,
+    aMultipleReadTextCalls ? "invokeReadTwiceId" : "invokeReadOnceId"
+  );
+}
+
+// @param aBrowser browser object of the content tab.
+function promiseMutatedReadResultFromContentElement(aBrowser) {
+  return promiseMutatedTextContentFromContentElement(aBrowser, "readResultId");
+}
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.events.asyncClipboard.clipboardItem", true],
+      ["test.events.async.enabled", true],
+    ],
+  });
+});
+
+add_task(async function test_paste_button_position() {
+  // Ensure there's text on the clipboard.
+  await promiseWritingRandomTextToClipboard();
+
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    const coordsOfClickInContentRelativeToScreenInDevicePixels =
+      await promiseClickContentToTriggerClipboardRead(browser, false);
+    info(
+      "coordsOfClickInContentRelativeToScreenInDevicePixels: " +
+        coordsOfClickInContentRelativeToScreenInDevicePixels.x +
+        ", " +
+        coordsOfClickInContentRelativeToScreenInDevicePixels.y
+    );
+
+    const pasteButtonCoordsRelativeToScreenInDevicePixels =
+      await pasteButtonIsShown;
+    info(
+      "pasteButtonCoordsRelativeToScreenInDevicePixels: " +
+        pasteButtonCoordsRelativeToScreenInDevicePixels.x +
+        ", " +
+        pasteButtonCoordsRelativeToScreenInDevicePixels.y
+    );
+
+    const mouseCoordsRelativeToScreenInDevicePixels =
+      getMouseCoordsRelativeToScreenInDevicePixels();
+    info(
+      "mouseCoordsRelativeToScreenInDevicePixels: " +
+        mouseCoordsRelativeToScreenInDevicePixels.x +
+        ", " +
+        mouseCoordsRelativeToScreenInDevicePixels.y
+    );
+
+    // Asserting not overlapping is important; otherwise, when the
+    // "Paste" button is shown via a `mousedown` event, the following
+    // `mouseup` event could accept the "Paste" button unnoticed by the
+    // user.
+    ok(
+      isCloselyLeftOnTopOf(
+        mouseCoordsRelativeToScreenInDevicePixels,
+        pasteButtonCoordsRelativeToScreenInDevicePixels
+      ),
+      "'Paste' button is closely left on top of the mouse pointer."
+    );
+    ok(
+      isCloselyLeftOnTopOf(
+        coordsOfClickInContentRelativeToScreenInDevicePixels,
+        pasteButtonCoordsRelativeToScreenInDevicePixels
+      ),
+      "Coords of click in content are closely left on top of the 'Paste' button."
+    );
+
+    // To avoid disturbing subsequent tests.
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    await promiseClickPasteButton();
+    await pasteButtonIsHidden;
+  });
+});
+
+add_task(async function test_accepting_paste_button() {
+  // Randomized text to avoid overlappings with other tests.
+  const clipboardText = await promiseWritingRandomTextToClipboard();
+
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    await promiseClickContentToTriggerClipboardRead(browser, false);
+    await pasteButtonIsShown;
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    const mutatedReadResultFromContentElement =
+      promiseMutatedReadResultFromContentElement(browser);
+    await promiseClickPasteButton();
+    await pasteButtonIsHidden;
+    await mutatedReadResultFromContentElement.then(value => {
+      is(
+        value,
+        "Resolved: " + clipboardText,
+        "Text returned from `navigator.clipboard.read()` is as expected."
+      );
+    });
+  });
+});
+
+add_task(async function test_dismissing_paste_button() {
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    await promiseClickContentToTriggerClipboardRead(browser, false);
+    await pasteButtonIsShown;
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    const mutatedReadResultFromContentElement =
+      promiseMutatedReadResultFromContentElement(browser);
+    await promiseDismissPasteButton();
+    await pasteButtonIsHidden;
+    await mutatedReadResultFromContentElement.then(value => {
+      is(
+        value,
+        "Rejected: The user dismissed the 'Paste' button.",
+        "`navigator.clipboard.read()` rejected after dismissing the 'Paste' button"
+      );
+    });
+  });
+});
+
+add_task(
+  async function test_multiple_read_invocations_for_same_user_activation() {
+    // Randomized text to avoid overlappings with other tests.
+    const clipboardText = await promiseWritingRandomTextToClipboard();
+
+    await BrowserTestUtils.withNewTab(
+      kContentFileUrl,
+      async function (browser) {
+        const pasteButtonIsShown = promisePasteButtonIsShown();
+        await promiseClickContentToTriggerClipboardRead(browser, true);
+        await pasteButtonIsShown;
+        const mutatedReadResultFromContentElement =
+          promiseMutatedReadResultFromContentElement(browser);
+        const pasteButtonIsHidden = promisePasteButtonIsHidden();
+        await promiseClickPasteButton();
+        await mutatedReadResultFromContentElement.then(value => {
+          is(
+            value,
+            "Resolved 1: " + clipboardText + "; Resolved 2: " + clipboardText,
+            "Two calls of `navigator.clipboard.read()` both resolved with the expected text."
+          );
+        });
+
+        // To avoid disturbing subsequent tests.
+        await pasteButtonIsHidden;
+      }
+    );
+  }
+);
+
+add_task(async function test_new_user_activation_shows_paste_button_again() {
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    // Ensure there's text on the clipboard.
+    await promiseWritingRandomTextToClipboard();
+
+    for (let i = 0; i < 2; ++i) {
+      const pasteButtonIsShown = promisePasteButtonIsShown();
+      // A click initiates a new user activation.
+      await promiseClickContentToTriggerClipboardRead(browser, false);
+      await pasteButtonIsShown;
+
+      const pasteButtonIsHidden = promisePasteButtonIsHidden();
+      await promiseClickPasteButton();
+      await pasteButtonIsHidden;
+    }
+  });
+});
diff --git a/dom/events/test/clipboard/browser_navigator_clipboard_readText.js b/dom/events/test/clipboard/browser_navigator_clipboard_readText.js
new file mode 100644
index 0000000000..7563fa8a21
--- /dev/null
+++ b/dom/events/test/clipboard/browser_navigator_clipboard_readText.js
@@ -0,0 +1,201 @@
+/* -*- Mode: JavaScript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const kBaseUrlForContent = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "https://example.com"
+);
+
+const kContentFileName = "simple_navigator_clipboard_readText.html";
+
+const kContentFileUrl = kBaseUrlForContent + kContentFileName;
+
+const kApzTestNativeEventUtilsUrl =
+  "chrome://mochitests/content/browser/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js";
+
+Services.scriptloader.loadSubScript(kApzTestNativeEventUtilsUrl, this);
+
+// @param aBrowser browser object of the content tab.
+// @param aMultipleReadTextCalls if false, exactly one call is made, two
+//                               otherwise.
+function promiseClickContentToTriggerClipboardReadText(
+  aBrowser,
+  aMultipleReadTextCalls
+) {
+  return promiseClickContentElement(
+    aBrowser,
+    aMultipleReadTextCalls ? "invokeReadTextTwiceId" : "invokeReadTextOnceId"
+  );
+}
+
+// @param aBrowser browser object of the content tab.
+function promiseMutatedReadTextResultFromContentElement(aBrowser) {
+  return promiseMutatedTextContentFromContentElement(
+    aBrowser,
+    "readTextResultId"
+  );
+}
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.events.asyncClipboard.readText", true],
+      ["test.events.async.enabled", true],
+    ],
+  });
+});
+
+add_task(async function test_paste_button_position() {
+  // Ensure there's text on the clipboard.
+  await promiseWritingRandomTextToClipboard();
+
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    const coordsOfClickInContentRelativeToScreenInDevicePixels =
+      await promiseClickContentToTriggerClipboardReadText(browser, false);
+    info(
+      "coordsOfClickInContentRelativeToScreenInDevicePixels: " +
+        coordsOfClickInContentRelativeToScreenInDevicePixels.x +
+        ", " +
+        coordsOfClickInContentRelativeToScreenInDevicePixels.y
+    );
+
+    const pasteButtonCoordsRelativeToScreenInDevicePixels =
+      await pasteButtonIsShown;
+    info(
+      "pasteButtonCoordsRelativeToScreenInDevicePixels: " +
+        pasteButtonCoordsRelativeToScreenInDevicePixels.x +
+        ", " +
+        pasteButtonCoordsRelativeToScreenInDevicePixels.y
+    );
+
+    const mouseCoordsRelativeToScreenInDevicePixels =
+      getMouseCoordsRelativeToScreenInDevicePixels();
+    info(
+      "mouseCoordsRelativeToScreenInDevicePixels: " +
+        mouseCoordsRelativeToScreenInDevicePixels.x +
+        ", " +
+        mouseCoordsRelativeToScreenInDevicePixels.y
+    );
+
+    // Asserting not overlapping is important; otherwise, when the
+    // "Paste" button is shown via a `mousedown` event, the following
+    // `mouseup` event could accept the "Paste" button unnoticed by the
+    // user.
+    ok(
+      isCloselyLeftOnTopOf(
+        mouseCoordsRelativeToScreenInDevicePixels,
+        pasteButtonCoordsRelativeToScreenInDevicePixels
+      ),
+      "'Paste' button is closely left on top of the mouse pointer."
+    );
+    ok(
+      isCloselyLeftOnTopOf(
+        coordsOfClickInContentRelativeToScreenInDevicePixels,
+        pasteButtonCoordsRelativeToScreenInDevicePixels
+      ),
+      "Coords of click in content are closely left on top of the 'Paste' button."
+    );
+
+    // To avoid disturbing subsequent tests.
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    await promiseClickPasteButton();
+    await pasteButtonIsHidden;
+  });
+});
+
+add_task(async function test_accepting_paste_button() {
+  // Randomized text to avoid overlappings with other tests.
+  const clipboardText = await promiseWritingRandomTextToClipboard();
+
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    await promiseClickContentToTriggerClipboardReadText(browser, false);
+    await pasteButtonIsShown;
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    const mutatedReadTextResultFromContentElement =
+      promiseMutatedReadTextResultFromContentElement(browser);
+    await promiseClickPasteButton();
+    await pasteButtonIsHidden;
+    await mutatedReadTextResultFromContentElement.then(value => {
+      is(
+        value,
+        "Resolved: " + clipboardText,
+        "Text returned from `navigator.clipboard.readText()` is as expected."
+      );
+    });
+  });
+});
+
+add_task(async function test_dismissing_paste_button() {
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    await promiseClickContentToTriggerClipboardReadText(browser, false);
+    await pasteButtonIsShown;
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    const mutatedReadTextResultFromContentElement =
+      promiseMutatedReadTextResultFromContentElement(browser);
+    await promiseDismissPasteButton();
+    await pasteButtonIsHidden;
+    await mutatedReadTextResultFromContentElement.then(value => {
+      is(
+        value,
+        "Rejected.",
+        "`navigator.clipboard.readText()` rejected after dismissing the 'Paste' button"
+      );
+    });
+  });
+});
+
+add_task(
+  async function test_multiple_readText_invocations_for_same_user_activation() {
+    // Randomized text to avoid overlappings with other tests.
+    const clipboardText = await promiseWritingRandomTextToClipboard();
+
+    await BrowserTestUtils.withNewTab(
+      kContentFileUrl,
+      async function (browser) {
+        const pasteButtonIsShown = promisePasteButtonIsShown();
+        await promiseClickContentToTriggerClipboardReadText(browser, true);
+        await pasteButtonIsShown;
+        const mutatedReadTextResultFromContentElement =
+          promiseMutatedReadTextResultFromContentElement(browser);
+        const pasteButtonIsHidden = promisePasteButtonIsHidden();
+        await promiseClickPasteButton();
+        await mutatedReadTextResultFromContentElement.then(value => {
+          is(
+            value,
+            "Resolved 1: " + clipboardText + "; Resolved 2: " + clipboardText,
+            "Two calls of `navigator.clipboard.read()` both resolved with the expected text."
+          );
+        });
+
+        // To avoid disturbing subsequent tests.
+        await pasteButtonIsHidden;
+      }
+    );
+  }
+);
+
+add_task(async function test_new_user_activation_shows_paste_button_again() {
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    // Ensure there's text on the clipboard.
+    await promiseWritingRandomTextToClipboard();
+
+    for (let i = 0; i < 2; ++i) {
+      const pasteButtonIsShown = promisePasteButtonIsShown();
+      // A click initiates a new user activation.
+      await promiseClickContentToTriggerClipboardReadText(browser, false);
+      await pasteButtonIsShown;
+
+      const pasteButtonIsHidden = promisePasteButtonIsHidden();
+      await promiseClickPasteButton();
+      await pasteButtonIsHidden;
+    }
+  });
+});
diff --git a/dom/events/test/clipboard/browser_navigator_clipboard_touch.js b/dom/events/test/clipboard/browser_navigator_clipboard_touch.js
new file mode 100644
index 0000000000..aeea9a612d
--- /dev/null
+++ b/dom/events/test/clipboard/browser_navigator_clipboard_touch.js
@@ -0,0 +1,114 @@
+/* -*- Mode: JavaScript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const kBaseUrlForContent = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "https://example.com"
+);
+const kContentFileUrl =
+  kBaseUrlForContent + "simple_navigator_clipboard_readText.html";
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js",
+  this
+);
+
+// @param aBrowser browser object of the content tab.
+// @param aContentElementId the ID of the element to be tapped.
+function promiseTouchTapContent(aBrowser, aContentElementId) {
+  return SpecialPowers.spawn(
+    aBrowser,
+    [aContentElementId],
+    async _contentElementId => {
+      await content.wrappedJSObject.waitUntilApzStable();
+
+      const contentElement = content.document.getElementById(_contentElementId);
+      let promise = new Promise(resolve => {
+        contentElement.addEventListener(
+          "click",
+          function (e) {
+            resolve({ x: e.screenX, y: e.screenY });
+          },
+          { once: true }
+        );
+      });
+
+      EventUtils.synthesizeTouchAtCenter(contentElement, {}, content.window);
+
+      return promise;
+    }
+  );
+}
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.events.asyncClipboard.readText", true],
+      ["test.events.async.enabled", true],
+    ],
+  });
+});
+
+add_task(async function test_paste_button_position_touch() {
+  // Ensure there's text on the clipboard.
+  await promiseWritingRandomTextToClipboard();
+
+  await BrowserTestUtils.withNewTab(kContentFileUrl, async function (browser) {
+    const pasteButtonIsShown = promisePasteButtonIsShown();
+    const coordsOfClickInContentRelativeToScreenInDevicePixels =
+      await promiseTouchTapContent(browser, "invokeReadTextOnceId");
+    info(
+      "coordsOfClickInContentRelativeToScreenInDevicePixels: " +
+        coordsOfClickInContentRelativeToScreenInDevicePixels.x +
+        ", " +
+        coordsOfClickInContentRelativeToScreenInDevicePixels.y
+    );
+
+    const pasteButtonCoordsRelativeToScreenInDevicePixels =
+      await pasteButtonIsShown;
+    info(
+      "pasteButtonCoordsRelativeToScreenInDevicePixels: " +
+        pasteButtonCoordsRelativeToScreenInDevicePixels.x +
+        ", " +
+        pasteButtonCoordsRelativeToScreenInDevicePixels.y
+    );
+
+    const mouseCoordsRelativeToScreenInDevicePixels =
+      getMouseCoordsRelativeToScreenInDevicePixels();
+    info(
+      "mouseCoordsRelativeToScreenInDevicePixels: " +
+        mouseCoordsRelativeToScreenInDevicePixels.x +
+        ", " +
+        mouseCoordsRelativeToScreenInDevicePixels.y
+    );
+
+    // Asserting not overlapping is important; otherwise, when the
+    // "Paste" button is shown via a `mousedown` event, the following
+    // `mouseup` event could accept the "Paste" button unnoticed by the
+    // user.
+    ok(
+      isCloselyLeftOnTopOf(
+        mouseCoordsRelativeToScreenInDevicePixels,
+        pasteButtonCoordsRelativeToScreenInDevicePixels
+      ),
+      "'Paste' button is closely left on top of the mouse pointer."
+    );
+    ok(
+      isCloselyLeftOnTopOf(
+        coordsOfClickInContentRelativeToScreenInDevicePixels,
+        pasteButtonCoordsRelativeToScreenInDevicePixels
+      ),
+      "Coords of click in content are closely left on top of the 'Paste' button."
+    );
+
+    // To avoid disturbing subsequent tests.
+    const pasteButtonIsHidden = promisePasteButtonIsHidden();
+    await promiseClickPasteButton();
+    await pasteButtonIsHidden;
+  });
+});
diff --git a/dom/events/test/clipboard/chrome.ini b/dom/events/test/clipboard/chrome.ini
new file mode 100644
index 0000000000..ce646f98ef
--- /dev/null
+++ b/dom/events/test/clipboard/chrome.ini
@@ -0,0 +1,3 @@
+[DEFAULT]
+
+[test_async_clipboard.xhtml]
diff --git a/dom/events/test/clipboard/head.js b/dom/events/test/clipboard/head.js
new file mode 100644
index 0000000000..0db1e0abf4
--- /dev/null
+++ b/dom/events/test/clipboard/head.js
@@ -0,0 +1,169 @@
+/* -*- Mode: JavaScript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const kPasteMenuPopupId = "clipboardReadPasteMenuPopup";
+const kPasteMenuItemId = "clipboardReadPasteMenuItem";
+
+function promiseWritingRandomTextToClipboard() {
+  const clipboardText = "X" + Math.random();
+  return navigator.clipboard.writeText(clipboardText).then(() => {
+    return clipboardText;
+  });
+}
+
+function promiseBrowserReflow() {
+  return new Promise(resolve =>
+    requestAnimationFrame(() => requestAnimationFrame(resolve))
+  );
+}
+
+function waitForPasteMenuPopupEvent(aEventSuffix) {
+  // The element with id `kPasteMenuPopupId` is inserted dynamically, hence
+  // calling `BrowserTestUtils.waitForEvent` instead of
+  // `BrowserTestUtils.waitForPopupEvent`.
+  return BrowserTestUtils.waitForEvent(
+    document,
+    "popup" + aEventSuffix,
+    false /* capture */,
+    e => {
+      return e.target.getAttribute("id") == kPasteMenuPopupId;
+    }
+  );
+}
+
+function promisePasteButtonIsShown() {
+  return waitForPasteMenuPopupEvent("shown").then(async () => {
+    ok(true, "Witnessed 'popupshown' event for 'Paste' button.");
+
+    const pasteButton = document.getElementById(kPasteMenuItemId);
+    ok(
+      pasteButton.disabled,
+      "Paste button should be shown with disabled by default"
+    );
+    await BrowserTestUtils.waitForMutationCondition(
+      pasteButton,
+      { attributeFilter: ["disabled"] },
+      () => !pasteButton.disabled,
+      "Wait for paste button enabled"
+    );
+
+    return promiseBrowserReflow().then(() => {
+      return coordinatesRelativeToScreen({
+        target: pasteButton,
+        offsetX: 0,
+        offsetY: 0,
+      });
+    });
+  });
+}
+
+function promisePasteButtonIsHidden() {
+  return waitForPasteMenuPopupEvent("hidden").then(() => {
+    ok(true, "Witnessed 'popuphidden' event for 'Paste' button.");
+    return promiseBrowserReflow();
+  });
+}
+
+function promiseClickPasteButton() {
+  const pasteButton = document.getElementById(kPasteMenuItemId);
+  let promise = BrowserTestUtils.waitForEvent(pasteButton, "click");
+  EventUtils.synthesizeMouseAtCenter(pasteButton, {});
+  return promise;
+}
+
+function getMouseCoordsRelativeToScreenInDevicePixels() {
+  let mouseXInCSSPixels = {};
+  let mouseYInCSSPixels = {};
+  window.windowUtils.getLastOverWindowPointerLocationInCSSPixels(
+    mouseXInCSSPixels,
+    mouseYInCSSPixels
+  );
+
+  return {
+    x:
+      (mouseXInCSSPixels.value + window.mozInnerScreenX) *
+      window.devicePixelRatio,
+    y:
+      (mouseYInCSSPixels.value + window.mozInnerScreenY) *
+      window.devicePixelRatio,
+  };
+}
+
+function isCloselyLeftOnTopOf(aCoordsP1, aCoordsP2, aDelta = 10) {
+  return (
+    Math.abs(aCoordsP2.x - aCoordsP1.x) < aDelta &&
+    Math.abs(aCoordsP2.y - aCoordsP1.y) < aDelta
+  );
+}
+
+function promiseDismissPasteButton() {
+  // nsXULPopupManager rollup is handled in widget code, so we have to
+  // synthesize native mouse events.
+  return EventUtils.promiseNativeMouseEvent({
+    type: "click",
+    target: document.body,
+    // Relies on the assumption that the center of chrome document doesn't
+    // overlay with the paste button showed for clipboard readText request.
+    atCenter: true,
+  });
+}
+
+// @param aBrowser browser object of the content tab.
+// @param aContentElementId the ID of the element to be clicked.
+function promiseClickContentElement(aBrowser, aContentElementId) {
+  return SpecialPowers.spawn(
+    aBrowser,
+    [aContentElementId],
+    async _contentElementId => {
+      const contentElement = content.document.getElementById(_contentElementId);
+      let promise = new Promise(resolve => {
+        contentElement.addEventListener(
+          "click",
+          function (e) {
+            resolve({ x: e.screenX, y: e.screenY });
+          },
+          { once: true }
+        );
+      });
+
+      EventUtils.synthesizeMouseAtCenter(contentElement, {}, content.window);
+
+      return promise;
+    }
+  );
+}
+
+// @param aBrowser browser object of the content tab.
+// @param aContentElementId the ID of the element to observe.
+function promiseMutatedTextContentFromContentElement(
+  aBrowser,
+  aContentElementId
+) {
+  return SpecialPowers.spawn(
+    aBrowser,
+    [aContentElementId],
+    async _contentElementId => {
+      const contentElement = content.document.getElementById(_contentElementId);
+
+      const promiseTextContentResult = new Promise(resolve => {
+        const mutationObserver = new content.MutationObserver(
+          (aMutationRecord, aMutationObserver) => {
+            info("Observed mutation.");
+            aMutationObserver.disconnect();
+            resolve(contentElement.textContent);
+          }
+        );
+
+        mutationObserver.observe(contentElement, {
+          childList: true,
+        });
+      });
+
+      return await promiseTextContentResult;
+    }
+  );
+}
diff --git a/dom/events/test/clipboard/simple_navigator_clipboard_keydown.html b/dom/events/test/clipboard/simple_navigator_clipboard_keydown.html
new file mode 100644
index 0000000000..15fcdfba2c
--- /dev/null
+++ b/dom/events/test/clipboard/simple_navigator_clipboard_keydown.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+  <head>
+  <meta charset="utf-8">
+  <script>
+    function onLoad() {
+      document.addEventListener("keydown", function() {
+        navigator.clipboard.readText();
+      });
+    }
+  </script>
+  </head>
+  <body onload="onLoad()">
+  </body>
+</html>
diff --git a/dom/events/test/clipboard/simple_navigator_clipboard_read.html b/dom/events/test/clipboard/simple_navigator_clipboard_read.html
new file mode 100644
index 0000000000..89f38a3240
--- /dev/null
+++ b/dom/events/test/clipboard/simple_navigator_clipboard_read.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<html>
+  <head>
+  <meta charset="utf-8">
+  <!-- Required by the .js part of the test. In a more ideal world, the script
+    could be loaded in the .js part; however, currently, that causes other
+    problems, which would require other changes in test framework code. -->
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/paint_listener.js"></script>
+  <script src="/tests/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js"></script>
+  <script src="/tests/gfx/layers/apz/test/mochitest/apz_test_utils.js"></script>
+
+  <script>
+    function onLoad() {
+      const readResult = document.getElementById("readResultId");
+
+      async function getClipboardText() {
+        let items = await navigator.clipboard.read();
+        if (items.length != 1) {
+          throw Error(`incorrect number of clipboard item (${items.length})`);
+          return;
+        }
+
+        let item = items[0];
+        for (let type of item.types) {
+          if (type == "text/plain") {
+            let blob = await item.getType(type);
+            return await blob.text();
+          }
+        }
+
+        throw Error("no text/plain type");
+      }
+
+      const b1 = document.getElementById("invokeReadOnceId");
+      b1.addEventListener("click", async () => {
+        getClipboardText().then(text => {
+          readResult.textContent = `Resolved: ${text}`;
+        }, (e) => { readResult.textContent = `Rejected: ${e.message}`});
+      });
+
+      const b2 = document.getElementById("invokeReadTwiceId");
+      b2.addEventListener("click", async () => {
+        const t1 = getClipboardText();
+        const t2 = getClipboardText();
+
+        const r1 = await t1.then(text => {
+          return `Resolved 1: ${text}`;
+        }, (e) => { return `Rejected 1: ${e.message}`;});
+
+        const r2 = await t2.then(text => {
+          return "Resolved 2: " + text;
+        }, (e) => { return `Rejected 2: ${e.message}`;});
+
+        readResult.textContent = r1 + "; " + r2;
+      });
+    }
+  </script>
+  </head>
+  <body onload="onLoad()">
+   <button id="invokeReadOnceId">1</button>
+   <button id="invokeReadTwiceId">2</button>
+   <div id="readResultId"/>
+  </body>
+</html>
diff --git a/dom/events/test/clipboard/simple_navigator_clipboard_readText.html b/dom/events/test/clipboard/simple_navigator_clipboard_readText.html
new file mode 100644
index 0000000000..0b85371091
--- /dev/null
+++ b/dom/events/test/clipboard/simple_navigator_clipboard_readText.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<html>
+  <head>
+  <meta charset="utf-8">
+  <!-- Required by the .js part of the test. In a more ideal world, the script
+    could be loaded in the .js part; however, currently, that causes other
+    problems, which would require other changes in test framework code. -->
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/paint_listener.js"></script>
+  <script src="/tests/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js"></script>
+  <script src="/tests/gfx/layers/apz/test/mochitest/apz_test_utils.js"></script>
+
+  <script>
+    function onLoad() {
+      const readTextResult = document.getElementById("readTextResultId");
+
+      const b1 = document.getElementById("invokeReadTextOnceId");
+      b1.addEventListener("click", async () => {
+        navigator.clipboard.readText().then(text => {
+          readTextResult.textContent = "Resolved: " + text;
+        }, () => { readTextResult.textContent = "Rejected." });
+      });
+
+      const b2 = document.getElementById("invokeReadTextTwiceId");
+      b2.addEventListener("click", async () => {
+        const t1 = navigator.clipboard.readText();
+        const t2 = navigator.clipboard.readText();
+
+        const r1 = await t1.then(text => {
+          return "Resolved 1: " + text;
+        }, () => { return "Rejected: 1";});
+
+        const r2 = await t2.then(text => {
+          return "Resolved 2: " + text;
+        }, () => { return "Rejected: 2";});
+
+        readTextResult.textContent = r1 + "; " + r2;
+      });
+    }
+  </script>
+  </head>
+  <body onload="onLoad()">
+   <button id="invokeReadTextOnceId">1</button>
+   <button id="invokeReadTextTwiceId">2</button>
+   <div id="readTextResultId"/>
+  </body>
+</html>
diff --git a/dom/events/test/clipboard/test_async_clipboard.xhtml b/dom/events/test/clipboard/test_async_clipboard.xhtml
new file mode 100644
index 0000000000..787821efc3
--- /dev/null
+++ b/dom/events/test/clipboard/test_async_clipboard.xhtml
@@ -0,0 +1,130 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css" type="text/css"?>
+
+<window title="Async clipboard APIs Test"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+        onload="runTest();">
+
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"/>
+
+<script class="testbody" type="application/javascript">
+<![CDATA[
+
+  SimpleTest.waitForExplicitFinish();
+
+  const Services = SpecialPowers.Services;
+  const { AppConstants } = SpecialPowers.ChromeUtils.import(
+    "resource://gre/modules/AppConstants.jsm"
+  );
+  const { PlacesUtils } = SpecialPowers.ChromeUtils.import(
+    "resource://gre/modules/PlacesUtils.jsm"
+  );
+
+  const kTextPlainMimeType = "text/plain";
+
+  function clearClipboard() {
+    Services.clipboard.emptyClipboard(Services.clipboard.kGlobalClipboard);
+  }
+
+  async function testRead() {
+    let expected = "x";
+    await SimpleTest.promiseClipboardChange(expected, () => {
+      SpecialPowers.clipboardCopyString(expected);
+    }, kTextPlainMimeType);
+    let items = await navigator.clipboard.read();
+    is(items.length, 1, "read() read exactly one item");
+    const actual = await items[0].getType(kTextPlainMimeType).then(blob => blob.text());
+    is(actual, expected, "read() read the right thing");
+  }
+
+  async function testWrite() {
+    await SimpleTest.promiseClipboardChange("", () => {
+      clearClipboard();
+    });
+
+    let expected = "x";
+    // eslint-disable-next-line no-undef
+    let item = new ClipboardItem({[kTextPlainMimeType]: expected});
+    await navigator.clipboard.write([item]);
+    let actual = SpecialPowers.getClipboardData(kTextPlainMimeType);
+    is(actual, expected, "write() wrote the right thing");
+  }
+
+  async function testReadText() {
+    let expected = "x";
+    await SimpleTest.promiseClipboardChange(expected, () => {
+      SpecialPowers.clipboardCopyString(expected);
+    }, kTextPlainMimeType);
+    let actual = await navigator.clipboard.readText();
+    is(actual, expected, "readText() read the right thing");
+  }
+
+  async function testWriteText() {
+    await SimpleTest.promiseClipboardChange("", () => {
+      clearClipboard();
+    });
+
+    let expected = "x";
+    await navigator.clipboard.writeText(expected);
+    let actual = SpecialPowers.getClipboardData(kTextPlainMimeType);
+    is(actual, expected, "writeText() wrote the right thing");
+  }
+
+  async function testNoContentsRead() {
+    await SimpleTest.promiseClipboardChange("", () => {
+      clearClipboard();
+    });
+
+    const items = await navigator.clipboard.read();
+
+    // Bug 1756955: at least on Ubuntu 20.04, clearing the clipboard leads to
+    // one item with no types.
+    if (!items.length ||
+        (items.length == 1 && !items[0].types.length)) {
+      ok(true, "read() read the right thing from empty clipboard");
+    } else {
+      ok(false, "read() read the wrong thing from empty clipboard");
+    }
+  }
+
+  async function testNoContentsReadText() {
+    await SimpleTest.promiseClipboardChange("", () => {
+      clearClipboard();
+    });
+    let actual = await navigator.clipboard.readText();
+    is(actual, "", "readText() read the right thing from empty clipboard");
+  }
+
+  function runTest() {
+    (async function() {
+      await SpecialPowers.pushPrefEnv({"set": [
+        ["dom.events.asyncClipboard.clipboardItem", true],
+      ]});
+      await testRead();
+      await testReadText();
+      await testWrite();
+      await testWriteText();
+
+      await testNoContentsRead();
+      await testNoContentsReadText();
+
+      SimpleTest.finish();
+    })();
+  }
+  ]]>
+</script>
+
+<body xmlns="http://www.w3.org/1999/xhtml">
+<p id="display">
+</p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+</pre>
+</body>
+
+</window>