Bug 1742714 - Get rid of nsIFormSubmitObserver; r=geckoview-reviewers,agi,smaug

Differential Revision: https://phabricator.services.mozilla.com/D132091

browser/actors/FormValidationChild.jsm

@@ -51,10 +51,6 @@ class FormValidationChild extends JSWindowActorChild {
     }
   }
 
-  /*
-   * nsIFormSubmitObserver
-   */
-
   notifyInvalidSubmit(aFormElement, aInvalidElements) {
     // Show a validation message on the first focusable element.
     for (let element of aInvalidElements) {

browser/modules/test/browser/formValidation/browser_form_validation.js

@@ -68,12 +68,6 @@ function checkPopupHide() {
   );
 }
 
-var gObserver = {
-  QueryInterface: ChromeUtils.generateQI(["nsIFormSubmitObserver"]),
-
-  notifyInvalidSubmit(aFormElement, aInvalidElements) {},
-};
-
 var testId = 0;
 
 function incrementTest() {
@@ -440,53 +434,6 @@ add_task(async function() {
   gBrowser.removeCurrentTab();
 });
 
-/**
- * In this test, we check that nothing happen if the invalid form is
- * submitted in a background tab.
- */
-add_task(async function() {
-  // Observers don't propagate currently across processes. We may add support for this in the
-  // future via the addon compat layer.
-  if (gMultiProcessBrowser) {
-    return;
-  }
-
-  incrementTest();
-  let uri =
-    getDocHeader() +
-    "<form target='t' action='data:text/html,'><input id='i' required><input id='s' type='submit'></form>" +
-    getDocFooter();
-  let browser = await openNewTab(uri, true);
-  isnot(
-    gBrowser.selectedBrowser,
-    browser,
-    "This tab should have been loaded in background"
-  );
-
-  let notifierPromise = new Promise((resolve, reject) => {
-    gObserver.notifyInvalidSubmit = function() {
-      executeSoon(function() {
-        checkPopupHide();
-
-        // Clean-up
-        Services.obs.removeObserver(gObserver, "invalidformsubmit");
-        gObserver.notifyInvalidSubmit = function() {};
-        resolve();
-      });
-    };
-
-    Services.obs.addObserver(gObserver, "invalidformsubmit");
-
-    executeSoon(function() {
-      browser.contentDocument.getElementById("s").click();
-    });
-  });
-
-  await notifierPromise;
-
-  gBrowser.removeTab(gBrowser.getTabForBrowser(browser));
-});
-
 /**
  * In this test, we check that the message is correctly updated when it changes.
  */

dom/html/HTMLFormElement.cpp

@@ -51,8 +51,6 @@
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_prompts.h"
 #include "mozilla/StaticPrefs_signon.h"
-#include "nsIFormSubmitObserver.h"
-#include "nsIObserverService.h"
 #include "nsCategoryManagerUtils.h"
 #include "nsIContentInlines.h"
 #include "nsISimpleEnumerator.h"
@@ -1876,27 +1874,18 @@ bool HTMLFormElement::CheckValidFormSubmission() {
    * invalid controls in the form.
    * This should not be done if the form has been submitted with .submit().
    *
-   * NOTE: for the moment, we are also checking that there is an observer for
-   * NS_INVALIDFORMSUBMIT_SUBJECT so it will prevent blocking form submission
-   * if the browser does not have implemented a UI yet.
+   * NOTE: for the moment, we are also checking that whether the MozInvalidForm
+   * event gets prevented default so it will prevent blocking form submission if
+   * the browser does not have implemented a UI yet.
    *
-   * TODO: the check for observer should be removed later when HTML5 Forms will
-   * be spread enough and authors will assume forms can't be submitted when
-   * invalid. See bug 587671.
+   * TODO: the check for MozInvalidForm event should be removed later when HTML5
+   * Forms will be spread enough and authors will assume forms can't be
+   * submitted when invalid. See bug 587671.
    */
 
   NS_ASSERTION(!HasAttr(kNameSpaceID_None, nsGkAtoms::novalidate),
                "We shouldn't be there if novalidate is set!");
 
-  // When .submit() is called aEvent = nullptr so we can rely on that to know if
-  // we have to check the validity of the form.
-  nsCOMPtr<nsIObserverService> service =
-      mozilla::services::GetObserverService();
-  if (!service) {
-    NS_WARNING("No observer service available!");
-    return true;
-  }
-
   AutoTArray<RefPtr<Element>, 32> invalidElements;
   if (CheckFormValidity(&invalidElements)) {
     return true;
@@ -1962,39 +1951,7 @@ bool HTMLFormElement::CheckValidFormSubmission() {
 
   DispatchEvent(*event);
 
-  bool result = !event->DefaultPrevented();
-
-  nsCOMPtr<nsISimpleEnumerator> theEnum;
-  nsresult rv = service->EnumerateObservers(NS_INVALIDFORMSUBMIT_SUBJECT,
-                                            getter_AddRefs(theEnum));
-  NS_ENSURE_SUCCESS(rv, result);
-
-  bool hasObserver = false;
-  rv = theEnum->HasMoreElements(&hasObserver);
-
-  if (NS_SUCCEEDED(rv) && hasObserver) {
-    result = false;
-
-    nsCOMPtr<nsISupports> inst;
-    nsCOMPtr<nsIFormSubmitObserver> observer;
-    bool more = true;
-    while (NS_SUCCEEDED(theEnum->HasMoreElements(&more)) && more) {
-      theEnum->GetNext(getter_AddRefs(inst));
-      observer = do_QueryInterface(inst);
-
-      if (observer) {
-        observer->NotifyInvalidSubmit(this, invalidElements);
-      }
-    }
-  }
-
-  if (result) {
-    NS_WARNING(
-        "There is no observer for \"invalidformsubmit\". \
-One should be implemented!");
-  }
-
-  return result;
+  return !event->DefaultPrevented();
 }
 
 void HTMLFormElement::UpdateValidity(bool aElementValidity) {

dom/html/moz.build

@@ -24,7 +24,6 @@ MOCHITEST_CHROME_MANIFESTS += [
 BROWSER_CHROME_MANIFESTS += ["test/browser.ini"]
 
 XPIDL_SOURCES += [
-    "nsIFormSubmitObserver.idl",
     "nsIMenuBuilder.idl",
 ]
 

dom/html/nsIConstraintValidation.cpp

@@ -16,9 +16,6 @@
 #include "nsISimpleEnumerator.h"
 #include "nsContentUtils.h"
 
-#include "nsIFormSubmitObserver.h"
-#include "nsIObserverService.h"
-
 const uint16_t nsIConstraintValidation::sContentSpecifiedMaxLengthMessage = 256;
 
 using namespace mozilla;
@@ -87,36 +84,6 @@ bool nsIConstraintValidation::ReportValidity() {
 
   element->DispatchEvent(*event);
 
-  nsCOMPtr<nsIObserverService> service =
-      mozilla::services::GetObserverService();
-  if (!service) {
-    NS_WARNING("No observer service available!");
-    return true;
-  }
-
-  nsCOMPtr<nsISimpleEnumerator> theEnum;
-  nsresult rv = service->EnumerateObservers(NS_INVALIDFORMSUBMIT_SUBJECT,
-                                            getter_AddRefs(theEnum));
-
-  // Return true on error here because that's what we always did
-  NS_ENSURE_SUCCESS(rv, true);
-
-  bool hasObserver = false;
-  rv = theEnum->HasMoreElements(&hasObserver);
-
-  NS_ENSURE_SUCCESS(rv, true);
-  nsCOMPtr<nsISupports> inst;
-  nsCOMPtr<nsIFormSubmitObserver> observer;
-  bool more = true;
-  while (NS_SUCCEEDED(theEnum->HasMoreElements(&more)) && more) {
-    theEnum->GetNext(getter_AddRefs(inst));
-    observer = do_QueryInterface(inst);
-
-    if (observer) {
-      observer->NotifyInvalidSubmit(nullptr, invalidElements);
-    }
-  }
-
   auto* inputElement = HTMLInputElement::FromNode(element);
   if (inputElement && inputElement->State().HasState(NS_EVENT_STATE_FOCUS)) {
     inputElement->UpdateValidityUIBits(true);

dom/html/nsIFormSubmitObserver.idl

@@ -1,25 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* 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/. */
-
-
-#include "nsISupports.idl"
-
-interface mozIDOMWindow;
-interface nsIURI;
-interface nsIArray;
-
-webidl HTMLFormElement;
-webidl Element;
-
-[scriptable, uuid(867cb7e7-835d-408b-9788-d2834d284e03)]
-interface nsIFormSubmitObserver: nsISupports
-{
-  void notifyInvalidSubmit(in HTMLFormElement formNode,
-                           in Array<Element> invalidElements);
-};
-
-%{C++
-#define NS_INVALIDFORMSUBMIT_SUBJECT "invalidformsubmit"
-%}

dom/html/test/forms/test_formnovalidate_attribute.html

@@ -46,96 +46,79 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=589696
 
 /** Test for Bug 589696 **/
 
-var os = SpecialPowers.Cc['@mozilla.org/observer-service;1']
-                      .getService(SpecialPowers.Ci.nsIObserverService);
-var observers = os.enumerateObservers("invalidformsubmit");
+document.getElementById('av').addEventListener("invalid", function(aEvent) {
+  aEvent.target.removeAttribute("invalid", arguments.callee, false);
+  ok(true, "formnovalidate should not apply on if not set on the submit " +
+           "control used for the submission");
+  document.getElementById('b').click();
+});
+
+document.getElementById('bv').addEventListener("invalid", function(aEvent) {
+  aEvent.target.removeAttribute("invalid", arguments.callee, false);
+  ok(true, "formnovalidate should not apply on if not set on the submit " +
+           "control used for the submission");
+  var c = document.getElementById('c');
+  c.focus();
+  synthesizeKey("KEY_Enter");
+});
+
+document.getElementById('c').addEventListener("invalid", function(aEvent) {
+  aEvent.target.removeAttribute("invalid", arguments.callee, false);
+  ok(true, "formnovalidate should only apply on submit controls");
+  document.getElementById('d').click();
+});
+
+document.forms[3].addEventListener("submit", function(aEvent) {
+  aEvent.target.removeAttribute("submit", arguments.callee, false);
+  ok(true, "formnovalidate applies if set on the submit control used for the submission");
+  document.getElementById('e').click();
+});
+
+document.forms[4].addEventListener("submit", function(aEvent) {
+  aEvent.target.removeAttribute("submit", arguments.callee, false);
+  ok(true, "formnovalidate applies if set on the submit control used for the submission");
+  SimpleTest.executeSoon(SimpleTest.finish);
+});
 
 /**
- * formnovalidate should prevent form validation if set on the submit control
- * used to submit the form.
- *
- * The following test should not be done if there is no observer for
- * "invalidformsubmit" because the form submission will not be canceled in that
- * case.
+ * We have to be sure invalid events behave as expected.
+ * They should be sent before the submit event so we can just create a test
+ * failure if we got one when unexpected. All of them should be caught if
+ * sent.
+ * At worst, we got random green which isn't harmful.
+ * If expected, they will be part of the chain reaction.
  */
-
-if (observers.hasMoreElements()) {
-  document.getElementById('av').addEventListener("invalid", function(aEvent) {
-    aEvent.target.removeAttribute("invalid", arguments.callee, false);
-    ok(true, "formnovalidate should not apply on if not set on the submit " +
-             "control used for the submission");
-    document.getElementById('b').click();
-  });
-
-  document.getElementById('bv').addEventListener("invalid", function(aEvent) {
-    aEvent.target.removeAttribute("invalid", arguments.callee, false);
-    ok(true, "formnovalidate should not apply on if not set on the submit " +
-             "control used for the submission");
-    var c = document.getElementById('c');
-    c.focus();
-    synthesizeKey("KEY_Enter");
-  });
-
-  document.getElementById('c').addEventListener("invalid", function(aEvent) {
-    aEvent.target.removeAttribute("invalid", arguments.callee, false);
-    ok(true, "formnovalidate should only apply on submit controls");
-    document.getElementById('d').click();
-  });
-
-  document.forms[3].addEventListener("submit", function(aEvent) {
-    aEvent.target.removeAttribute("submit", arguments.callee, false);
-    ok(true, "formnovalidate applies if set on the submit control used for the submission");
-    document.getElementById('e').click();
-  });
-
-  document.forms[4].addEventListener("submit", function(aEvent) {
-    aEvent.target.removeAttribute("submit", arguments.callee, false);
-    ok(true, "formnovalidate applies if set on the submit control used for the submission");
-    SimpleTest.executeSoon(SimpleTest.finish);
-  });
-
-  /**
-   * We have to be sure invalid events behave as expected.
-   * They should be sent before the submit event so we can just create a test
-   * failure if we got one when unexpected. All of them should be caught if
-   * sent.
-   * At worst, we got random green which isn't harmful.
-   * If expected, they will be part of the chain reaction.
-   */
-  function unexpectedInvalid(aEvent)
-  {
-    aEvent.target.removeAttribute("invalid", unexpectedInvalid, false);
-    ok(false, "invalid event should not be sent");
-  }
-
-  document.getElementById('dv').addEventListener("invalid", unexpectedInvalid);
-  document.getElementById('ev').addEventListener("invalid", unexpectedInvalid);
-
-  /**
-   * Some submission have to be canceled. In that case, the submit events should
-   * not be sent.
-   * Same behavior as unexpected invalid events.
-   */
-  function unexpectedSubmit(aEvent)
-  {
-    aEvent.target.removeAttribute("submit", unexpectedSubmit, false);
-    ok(false, "submit event should not be sent");
-  }
-
-  document.forms[0].addEventListener("submit", unexpectedSubmit);
-  document.forms[1].addEventListener("submit", unexpectedSubmit);
-  document.forms[2].addEventListener("submit", unexpectedSubmit);
-
-  SimpleTest.waitForExplicitFinish();
-
-  // This is going to call all the tests (with a chain reaction).
-  SimpleTest.waitForFocus(function() {
-    document.getElementById('a').click();
-  });
-} else {
-  todo(false, "No 'invalidformsubmit' observers. Skip test.");
+function unexpectedInvalid(aEvent)
+{
+  aEvent.target.removeAttribute("invalid", unexpectedInvalid, false);
+  ok(false, "invalid event should not be sent");
 }
 
+document.getElementById('dv').addEventListener("invalid", unexpectedInvalid);
+document.getElementById('ev').addEventListener("invalid", unexpectedInvalid);
+
+/**
+ * Some submission have to be canceled. In that case, the submit events should
+ * not be sent.
+ * Same behavior as unexpected invalid events.
+ */
+function unexpectedSubmit(aEvent)
+{
+  aEvent.target.removeAttribute("submit", unexpectedSubmit, false);
+  ok(false, "submit event should not be sent");
+}
+
+document.forms[0].addEventListener("submit", unexpectedSubmit);
+document.forms[1].addEventListener("submit", unexpectedSubmit);
+document.forms[2].addEventListener("submit", unexpectedSubmit);
+
+SimpleTest.waitForExplicitFinish();
+
+// This is going to call all the tests (with a chain reaction).
+SimpleTest.waitForFocus(function() {
+  document.getElementById('a').click();
+});
+
 </script>
 </pre>
 </body>

dom/html/test/forms/test_novalidate_attribute.html

@@ -34,9 +34,10 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=556013
 /**
  * novalidate should prevent form validation, thus not blocking form submission.
  *
- * NOTE: if there is no invalidformsubmit observer, the form submission will
- * never be blocked and this test might be a false-positive but that should not
- * be a problem.
+ * NOTE: if the MozInvalidForm event doesn't get prevented default, the form
+ * submission will never be blocked and this test might be a false-positive but
+ * that should not be a problem. We will remove the check for MozInvalidForm
+ * event, see bug 587671.
  */
 document.forms[0].addEventListener("submit", function(aEvent) {
   ok(true, "novalidate has been correctly used for first form");

dom/html/test/test_bug605124-1.html

@@ -41,65 +41,57 @@ function checkPseudoClass(aElement, aExpected)
      "matches(':-moz-ui-invalid') should return " + aExpected + " for " + aElement);
 }
 
-var os = SpecialPowers.Cc['@mozilla.org/observer-service;1']
-                      .getService(SpecialPowers.Ci.nsIObserverService);
-var observers = os.enumerateObservers("invalidformsubmit");
+var content = document.getElementById('content');
+var textarea = document.getElementsByTagName('textarea')[0];
+var input = document.getElementsByTagName('input')[0];
+var select = document.getElementsByTagName('select')[0];
+var button = document.getElementsByTagName('button')[0];
+var form = document.forms[0];
 
-if (observers.hasMoreElements()) {
-  var content = document.getElementById('content');
-  var textarea = document.getElementsByTagName('textarea')[0];
-  var input = document.getElementsByTagName('input')[0];
-  var select = document.getElementsByTagName('select')[0];
-  var button = document.getElementsByTagName('button')[0];
-  var form = document.forms[0];
+checkPseudoClass(textarea, false);
+checkPseudoClass(input, false);
+checkPseudoClass(select, false);
 
-  checkPseudoClass(textarea, false);
-  checkPseudoClass(input, false);
-  checkPseudoClass(select, false);
+// Try to submit.
+button.click();
+checkPseudoClass(textarea, true);
+checkPseudoClass(input, true);
+checkPseudoClass(select, true);
 
-  // Try to submit.
-  button.click();
-  checkPseudoClass(textarea, true);
-  checkPseudoClass(input, true);
-  checkPseudoClass(select, true);
+// No longer in the form.
+content.appendChild(textarea);
+content.appendChild(input);
+content.appendChild(select);
+checkPseudoClass(textarea, false);
+checkPseudoClass(input, false);
+checkPseudoClass(select, false);
 
-  // No longer in the form.
-  content.appendChild(textarea);
-  content.appendChild(input);
-  content.appendChild(select);
-  checkPseudoClass(textarea, false);
-  checkPseudoClass(input, false);
-  checkPseudoClass(select, false);
+// Back in the form.
+form.appendChild(textarea);
+form.appendChild(input);
+form.appendChild(select);
+checkPseudoClass(textarea, true);
+checkPseudoClass(input, true);
+checkPseudoClass(select, true);
 
-  // Back in the form.
-  form.appendChild(textarea);
-  form.appendChild(input);
-  form.appendChild(select);
-  checkPseudoClass(textarea, true);
-  checkPseudoClass(input, true);
-  checkPseudoClass(select, true);
+/* Case when elements get orphaned. */
+var textarea = document.getElementsByTagName('textarea')[1];
+var input = document.getElementsByTagName('input')[1];
+var select = document.getElementsByTagName('select')[1];
+var button = document.getElementsByTagName('button')[1];
+var form = document.forms[1];
 
-  /* Case when elements get orphaned. */
-  var textarea = document.getElementsByTagName('textarea')[1];
-  var input = document.getElementsByTagName('input')[1];
-  var select = document.getElementsByTagName('select')[1];
-  var button = document.getElementsByTagName('button')[1];
-  var form = document.forms[1];
+// Try to submit.
+button.click();
+checkPseudoClass(textarea, true);
+checkPseudoClass(input, true);
+checkPseudoClass(select, true);
 
-  // Try to submit.
-  button.click();
-  checkPseudoClass(textarea, true);
-  checkPseudoClass(input, true);
-  checkPseudoClass(select, true);
-
-  // Remove the form.
-  document.getElementsByTagName('table')[0].removeChild(form);
-  checkPseudoClass(textarea, false);
-  checkPseudoClass(input, false);
-  checkPseudoClass(select, false);
-} else {
-  todo(false, "No 'invalidformsubmit' observers. Skip test.");
-}
+// Remove the form.
+document.getElementsByTagName('table')[0].removeChild(form);
+checkPseudoClass(textarea, false);
+checkPseudoClass(input, false);
+checkPseudoClass(select, false);
 
 </script>
 </pre>

dom/html/test/test_bug605125-1.html

@@ -47,65 +47,57 @@ function checkPseudoClass(aElement, aExpected)
      "matches(':-moz-ui-valid') should return " + aExpected + " for " + aElement);
 }
 
-var os = SpecialPowers.Cc['@mozilla.org/observer-service;1']
-                      .getService(SpecialPowers.Ci.nsIObserverService);
-var observers = os.enumerateObservers("invalidformsubmit");
+var content = document.getElementById('content');
+var textarea = document.getElementsByTagName('textarea')[0];
+var input = document.getElementsByTagName('input')[0];
+var button = document.getElementsByTagName('button')[0];
+var select = document.getElementsByTagName('select')[0];
+var form = document.forms[0];
 
-if (observers.hasMoreElements()) {
-  var content = document.getElementById('content');
-  var textarea = document.getElementsByTagName('textarea')[0];
-  var input = document.getElementsByTagName('input')[0];
-  var button = document.getElementsByTagName('button')[0];
-  var select = document.getElementsByTagName('select')[0];
-  var form = document.forms[0];
+checkPseudoClass(textarea, false);
+checkPseudoClass(input, false);
+checkPseudoClass(select, false);
 
-  checkPseudoClass(textarea, false);
-  checkPseudoClass(input, false);
-  checkPseudoClass(select, false);
+// Try to submit.
+button.click();
+checkPseudoClass(textarea, true);
+checkPseudoClass(input, true);
+checkPseudoClass(select, true);
 
-  // Try to submit.
-  button.click();
-  checkPseudoClass(textarea, true);
-  checkPseudoClass(input, true);
-  checkPseudoClass(select, true);
+// No longer in the form.
+content.appendChild(textarea);
+content.appendChild(input);
+content.appendChild(select);
+checkPseudoClass(textarea, false);
+checkPseudoClass(input, false);
+checkPseudoClass(select, false);
 
-  // No longer in the form.
-  content.appendChild(textarea);
-  content.appendChild(input);
-  content.appendChild(select);
-  checkPseudoClass(textarea, false);
-  checkPseudoClass(input, false);
-  checkPseudoClass(select, false);
+// Back in the form.
+form.appendChild(textarea);
+form.appendChild(input);
+form.appendChild(select);
+checkPseudoClass(textarea, true);
+checkPseudoClass(input, true);
+checkPseudoClass(select, true);
 
-  // Back in the form.
-  form.appendChild(textarea);
-  form.appendChild(input);
-  form.appendChild(select);
-  checkPseudoClass(textarea, true);
-  checkPseudoClass(input, true);
-  checkPseudoClass(select, true);
+/* Case when elements get orphaned. */
+var textarea = document.getElementsByTagName('textarea')[1];
+var input = document.getElementsByTagName('input')[1];
+var button = document.getElementsByTagName('button')[1];
+var select = document.getElementsByTagName('select')[1];
+var form = document.forms[1];
 
-  /* Case when elements get orphaned. */
-  var textarea = document.getElementsByTagName('textarea')[1];
-  var input = document.getElementsByTagName('input')[1];
-  var button = document.getElementsByTagName('button')[1];
-  var select = document.getElementsByTagName('select')[1];
-  var form = document.forms[1];
+// Try to submit.
+button.click();
+checkPseudoClass(textarea, true);
+checkPseudoClass(input, true);
+checkPseudoClass(select, true);
 
-  // Try to submit.
-  button.click();
-  checkPseudoClass(textarea, true);
-  checkPseudoClass(input, true);
-  checkPseudoClass(select, true);
-
-  // Remove the form.
-  document.getElementsByTagName('table')[0].removeChild(form);
-  checkPseudoClass(textarea, false);
-  checkPseudoClass(input, false);
-  checkPseudoClass(select, false);
-} else {
-  todo(false, "No 'invalidformsubmit' observers. Skip test.");
-}
+// Remove the form.
+document.getElementsByTagName('table')[0].removeChild(form);
+checkPseudoClass(textarea, false);
+checkPseudoClass(input, false);
+checkPseudoClass(select, false);
 
 </script>
 </pre>

mobile/android/actors/GeckoViewFormValidationChild.jsm

@@ -0,0 +1,25 @@
+/* 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 { GeckoViewActorChild } = ChromeUtils.import(
+  "resource://gre/modules/GeckoViewActorChild.jsm"
+);
+
+const EXPORTED_SYMBOLS = ["GeckoViewFormValidationChild"];
+
+class GeckoViewFormValidationChild extends GeckoViewActorChild {
+  handleEvent(aEvent) {
+    switch (aEvent.type) {
+      case "MozInvalidForm": {
+        // Handle invalid form submission. If we don't hook up to this,
+        // invalid forms are allowed to be submitted!
+        aEvent.preventDefault();
+        // We should show the validation message, bug 1510450.
+        break;
+      }
+    }
+  }
+}

mobile/android/actors/moz.build

@@ -11,6 +11,7 @@ FINAL_TARGET_FILES.actors += [
     "GeckoViewAutoFillChild.jsm",
     "GeckoViewContentChild.jsm",
     "GeckoViewContentParent.jsm",
+    "GeckoViewFormValidationChild.jsm",
     "GeckoViewPromptChild.jsm",
     "GeckoViewSettingsChild.jsm",
     "LoadURIDelegateChild.jsm",

mobile/android/components/geckoview/GeckoViewStartup.jsm

@@ -38,6 +38,15 @@ const JSWINDOWACTORS = {
     },
     allFrames: true,
   },
+  GeckoViewFormValidation: {
+    child: {
+      moduleURI: "resource:///actors/GeckoViewFormValidationChild.jsm",
+      events: {
+        MozInvalidForm: {},
+      },
+    },
+    allFrames: true,
+  },
 };
 
 class GeckoViewStartup {
@@ -124,21 +133,6 @@ class GeckoViewStartup {
           }
         );
 
-        // Handle invalid form submission. If we don't hook up to this,
-        // invalid forms are allowed to be submitted!
-        Services.obs.addObserver(
-          {
-            QueryInterface: ChromeUtils.generateQI([
-              "nsIObserver",
-              "nsIFormSubmitObserver",
-            ]),
-            notifyInvalidSubmit: (form, element) => {
-              // We should show the validation message here, bug 1510450.
-            },
-          },
-          "invalidformsubmit"
-        );
-
         if (
           Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_DEFAULT
         ) {