refactor: removed IE leftovers from src\client\core (#8000)

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## Purpose
_Describe the problem you want to address or the feature you want to
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## Approach
_Describe how your changes address the issue or implement the desired
functionality in as much detail as possible._

## References
_Provide a link to the existing issue(s), if any._

## Pre-Merge TODO
- [ ] Write tests for your proposed changes
- [ ] Make sure that existing tests do not fail

src/client/core/prevent-real-events.js

@@ -6,17 +6,11 @@ import {
 
 import scrollController from './scroll/controller';
 
-import { get, hasDimensions } from './utils/style';
-import { filter } from './utils/array';
-import {
-    isShadowUIElement,
-    isWindow,
-    getParents,
-} from './utils/dom';
+import { hasDimensions } from './utils/style';
+import { isShadowUIElement } from './utils/dom';
 
-const browserUtils   = utils.browser;
-const listeners      = eventSandbox.listeners;
-const eventSimulator = eventSandbox.eventSimulator;
+const browserUtils = utils.browser;
+const listeners    = eventSandbox.listeners;
 
 const PREVENTED_EVENTS = [
     'click', 'mousedown', 'mouseup', 'dblclick', 'contextmenu', 'mousemove', 'mouseover', 'mouseout',
@@ -47,35 +41,11 @@ function preventRealEventHandler (e, dispatched, preventDefault, cancelHandlers,
         }
 
         // NOTE: if an element loses focus because of becoming invisible, the blur event is
-        // raised. We must not prevent this blur event. In IE, an element loses focus only
-        // if the CSS 'display' property is set to 'none', other ways of making an element
-        // invisible don't lead to blurring (in MSEdge, focus/blur are sync).
-        if (e.type === 'blur') {
-            if (browserUtils.isIE && browserUtils.version < 12) {
-                const isWindowInstance   = isWindow(target);
-                const isElementInvisible = !isWindowInstance && get(target, 'display') === 'none';
-                let elementParents       = null;
-                let invisibleParents     = false;
-
-                if (!isWindowInstance && !isElementInvisible) {
-                    elementParents   = getParents(target);
-                    invisibleParents = filter(elementParents, parent => get(parent, 'display') === 'none');
-                }
-
-                if (isElementInvisible || invisibleParents.length) {
-                    // NOTE: In IE we should prevent the event and raise it on timeout. This is a fix for
-                    // the case when a focus event leads to the element disappearing. If we don't prevent
-                    // the blur event it will be raised before the previous focus event is raised (see B254768)
-                    eventSandbox.timers.deferFunction(() => {
-                        eventSimulator.blur(target);
-                    });
-                }
-            }
-            // NOTE: fix for a jQuery bug. An exception is raised when calling .is(':visible')
-            // for a window or document on page loading (when e.ownerDocument is null).
-            else if (target !== window && target !== window.document && !hasDimensions(target))
-                return;
-        }
+        // raised. We must not prevent this blur event.
+        // NOTE: fix for a jQuery bug. An exception is raised when calling .is(':visible')
+        // for a window or document on page loading (when e.ownerDocument is null).
+        if (e.type === 'blur' && target !== window && target !== window.document && !hasDimensions(target))
+            return;
 
         preventDefault();
     }

src/client/core/utils/dom.js

@@ -40,7 +40,6 @@ export const isMapElement                           = hammerhead.utils.dom.isMap
 export const isBodyElement                          = hammerhead.utils.dom.isBodyElement;
 export const isHtmlElement                          = hammerhead.utils.dom.isHtmlElement;
 export const isDocument                             = hammerhead.utils.dom.isDocument;
-export const isWindow                               = hammerhead.utils.dom.isWindow;
 export const isTextEditableInput                    = hammerhead.utils.dom.isTextEditableInput;
 export const isTextEditableElement                  = hammerhead.utils.dom.isTextEditableElement;
 export const isTextEditableElementAndEditingAllowed = hammerhead.utils.dom.isTextEditableElementAndEditingAllowed;
@@ -75,7 +74,7 @@ function canFocus (element, parent, tabIndex) {
     if (getElementStyleProperty(element, 'display') === 'none' || getElementStyleProperty(element, 'visibility') === 'hidden')
         return false;
 
-    if ((browserUtils.isIE || browserUtils.isAndroid) && isOptionElement(element))
+    if (browserUtils.isAndroid && isOptionElement(element))
         return false;
 
     if (tabIndex !== null && tabIndex < 0)
@@ -127,33 +126,23 @@ function filterFocusableElements (parent) {
     let tagName  = null;
     let tabIndex = null;
 
-    let needPush = false;
-
     for (let i = 0; i < allElements.length; i++) {
         element  = allElements[i];
         tagName  = getTagName(element);
         tabIndex = getTabIndexAttributeIntValue(element);
-        needPush = false;
 
         if (!canFocus(element, parent, tabIndex))
             continue;
 
-        if (inputElementsRegExp.test(tagName))
-            needPush = true;
-        else if (element.shadowRoot)
-            needPush = true;
-        else if (isIframeElement(element))
-            needPush = true;
-        else if (isAnchorElement(element) && element.hasAttribute('href'))
-            needPush = element.getAttribute('href') !== '' || !browserUtils.isIE || tabIndex !== null;
-
         const contentEditableAttr = element.getAttribute('contenteditable');
 
-        if (contentEditableAttr === '' || contentEditableAttr === 'true')
-            needPush = true;
-
-        if (tabIndex !== null)
-            needPush = true;
+        const needPush = inputElementsRegExp.test(tagName)
+                          || element.shadowRoot
+                          || isIframeElement(element)
+                          || isAnchorElement(element) && element.hasAttribute('href')
+                          || contentEditableAttr === ''
+                          || contentEditableAttr === 'true'
+                          || tabIndex !== null;
 
         if (needPush)
             focusableElements.push(element);
@@ -265,8 +254,6 @@ export function blocksImplicitSubmission (el) {
         inputTypeRegExp = /^(text|password|color|date|time|datetime|datetime-local|email|month|number|search|tel|url|week|image)$/i;
     else if (browserUtils.isFirefox)
         inputTypeRegExp = /^(text|password|date|time|datetime|datetime-local|email|month|number|search|tel|url|week|image)$/i;
-    else if (browserUtils.isIE)
-        inputTypeRegExp = /^(text|password|color|date|time|datetime|datetime-local|email|file|month|number|search|tel|url|week|image)$/i;
     else
         inputTypeRegExp = /^(text|password|datetime|email|number|search|tel|url|image)$/i;
 
@@ -358,11 +345,6 @@ export function remove (el) {
 }
 
 export function isIFrameWindowInDOM (win) {
-    //NOTE: In MS Edge, if an iframe is removed from DOM, the browser throws an exception when accessing window.top
-    //and window.frameElement. Fortunately, setTimeout is set to undefined in this case.
-    if (!win.setTimeout)
-        return false;
-
     let frameElement = null;
 
     try {
@@ -382,13 +364,7 @@ export function isIFrameWindowInDOM (win) {
 }
 
 export function isTopWindow (win) {
-    try {
-        //NOTE: MS Edge throws an exception when trying to access window.top from an iframe removed from DOM
-        return win.top === win;
-    }
-    catch (e) {
-        return false;
-    }
+    return win.top === win;
 }
 
 export function findIframeByWindow (iframeWindow) {