WebUI: Remove KeyboardEvent.key polyfil for iOS, no longer needed.

The polyfil was added 4 years ago at r403715. It is now supported by
iOS Safari for quite a few versions (10.3+), based on [1]

[1] https://caniuse.com/?search=KeyboardEvent.Key

Bug: None
Change-Id: I7e16c08b5f18f70342d69c270da4ec2f8a96aacd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2509929Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Auto-Submit: dpapad <dpapad@chromium.org>
Commit-Queue: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824098}

ui/webui/resources/js/util.js

@@ -322,110 +322,6 @@
   });
 }
 
-// <if expr="is_ios">
-// Polyfill 'key' in KeyboardEvent for iOS.
-// This function is not intended to be complete but should
-// be sufficient enough to have iOS work correctly while
-// it does not support key yet.
-if (!('key' in KeyboardEvent.prototype)) {
-  Object.defineProperty(KeyboardEvent.prototype, 'key', {
-    /** @this {KeyboardEvent} */
-    get() {
-      // 0-9
-      if (this.keyCode >= 0x30 && this.keyCode <= 0x39) {
-        return String.fromCharCode(this.keyCode);
-      }
-
-      // A-Z
-      if (this.keyCode >= 0x41 && this.keyCode <= 0x5a) {
-        let result = String.fromCharCode(this.keyCode).toLowerCase();
-        if (this.shiftKey) {
-          result = result.toUpperCase();
-        }
-        return result;
-      }
-
-      // Special characters
-      switch (this.keyCode) {
-        case 0x08:
-          return 'Backspace';
-        case 0x09:
-          return 'Tab';
-        case 0x0d:
-          return 'Enter';
-        case 0x10:
-          return 'Shift';
-        case 0x11:
-          return 'Control';
-        case 0x12:
-          return 'Alt';
-        case 0x1b:
-          return 'Escape';
-        case 0x20:
-          return ' ';
-        case 0x21:
-          return 'PageUp';
-        case 0x22:
-          return 'PageDown';
-        case 0x23:
-          return 'End';
-        case 0x24:
-          return 'Home';
-        case 0x25:
-          return 'ArrowLeft';
-        case 0x26:
-          return 'ArrowUp';
-        case 0x27:
-          return 'ArrowRight';
-        case 0x28:
-          return 'ArrowDown';
-        case 0x2d:
-          return 'Insert';
-        case 0x2e:
-          return 'Delete';
-        case 0x5b:
-          return 'Meta';
-        case 0x70:
-          return 'F1';
-        case 0x71:
-          return 'F2';
-        case 0x72:
-          return 'F3';
-        case 0x73:
-          return 'F4';
-        case 0x74:
-          return 'F5';
-        case 0x75:
-          return 'F6';
-        case 0x76:
-          return 'F7';
-        case 0x77:
-          return 'F8';
-        case 0x78:
-          return 'F9';
-        case 0x79:
-          return 'F10';
-        case 0x7a:
-          return 'F11';
-        case 0x7b:
-          return 'F12';
-        case 0xbb:
-          return '=';
-        case 0xbd:
-          return '-';
-        case 0xdb:
-          return '[';
-        case 0xdd:
-          return ']';
-      }
-      return 'Unidentified';
-    }
-  });
-} else {
-  window.console.log('KeyboardEvent.Key polyfill not required');
-}
-// </if>  /* is_ios */
-
 /**
  * @param {!Event} e
  * @return {boolean} Whether a modifier key was down when processing |e|.