Merge .eslintrc.js in core/script/layered_api/ subdirectories into one

elements/toast/.eslintrc.js and kv-storage/.eslintrc.js were identical,
and elements/virtual-scroller/.eslintrc.js had some differences.  The
following describes differences between them and decision for them.

* virtual-scroller had '2' for no-magic-numbers exceptions.
 We keep the '2' exception.

* virtual-scroller enabled max-len.
 We enable max-len.
 max-len is helpful because clang-format doesn't support *.mjs extension
 for now.

* virtual-scroller had no no-lonely-if and no no-else-return.
 We drop them.
 Following these rules is sometimes harmful for code consistency.

Change-Id: Icf3118e4d504248a55a284a763f7392c59793769
Bug: 976576
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1727447
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Reviewed-by: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683107}

third_party/blink/renderer/core/script/resources/layered_api/elements/toast/.eslintrc.js → third_party/blink/renderer/core/script/resources/layered_api/.eslintrc.js

@@ -73,7 +73,6 @@ module.exports = {
     'no-caller': 'error',
     'no-case-declarations': 'error',
     'no-div-regex': 'off',
-    'no-else-return': 'error',
     'no-empty-function': 'off',
     'no-empty-pattern': 'error',
     'no-eq-null': 'error',
@@ -94,7 +93,7 @@ module.exports = {
     'no-labels': ['error', {allowLoop: true}],
     'no-lone-blocks': 'error',
     'no-loop-func': 'error',
-    'no-magic-numbers': ['error', {ignore: [0, 1]}],
+    'no-magic-numbers': ['error', {ignore: [0, 1, 2]}],
     'no-multi-spaces': ['error', {ignoreEOLComments: true}],
     'no-multi-str': 'error',
     'no-new': 'error',
@@ -204,7 +203,9 @@ module.exports = {
     'linebreak-style': ['error', 'unix'],
     'lines-around-comment': 'off',
     'max-depth': 'off',
-    'max-len': 'off',
+    'max-len': ['error', {
+        tabWidth: 2,
+        ignorePattern: "(^import |// eslint-disable-line |https?://)"}],
     'max-lines': 'off',
     'max-nested-callbacks': 'off',
     'max-params': 'off',
@@ -218,7 +219,6 @@ module.exports = {
     'no-bitwise': 'off',
     'no-continue': 'off',
     'no-inline-comments': 'off',
-    'no-lonely-if': 'error',
     'no-mixed-operators': [
       'error',
       {

third_party/blink/renderer/core/script/resources/layered_api/elements/internal/reflection.mjs

@@ -17,12 +17,12 @@
  *     this argument is omitted.
  */
 export function installBool(proto, attrName, propName = attrName) {
-  let getter = function() {
+  function getter() {
     return this.hasAttribute(attrName);
-  };
-  let setter = function(value) {
+  }
+  function setter(value) {
     this.toggleAttribute(attrName, Boolean(value));
-  };
+  }
   Object.defineProperty(
       getter, 'name',
       {configurable: true, enumerable: false, value: 'get ' + propName});
@@ -44,13 +44,13 @@ export function installBool(proto, attrName, propName = attrName) {
  *     this argument is omitted.
  */
 export function installString(proto, attrName, propName = attrName) {
-  let getter = function() {
-    let value = this.getAttribute(attrName);
+  function getter() {
+    const value = this.getAttribute(attrName);
     return value === null ? '' : value;
-  };
-  let setter = function(value) {
+  }
+  function setter(value) {
     this.setAttribute(attrName, value);
-  };
+  }
   Object.defineProperty(
       getter, 'name',
       {configurable: true, enumerable: false, value: 'get ' + propName});

third_party/blink/renderer/core/script/resources/layered_api/elements/switch/face_utils.mjs

@@ -37,36 +37,36 @@ function installGetter(proto, propName, getter) {
 export function installPropertiesAndFunctions(proto, internals) {
   reflection.installBool(proto, 'disabled');
   reflection.installString(proto, 'name');
-  installGetter(proto, 'type', function() {
+  installGetter(proto, 'type', function () {
     if (!(this instanceof proto.constructor)) {
-      throw TypeError(
+      throw new TypeError(
           'The context object is not an instance of ' + proto.contructor.name);
     }
     return this.localName;
   });
 
-  installGetter(proto, 'form', function() {
+  installGetter(proto, 'form', function () {
     return this[internals].form;
   });
-  installGetter(proto, 'willValidate', function() {
+  installGetter(proto, 'willValidate', function () {
     return this[internals].willValidate;
   });
-  installGetter(proto, 'validity', function() {
+  installGetter(proto, 'validity', function () {
     return this[internals].validity;
   });
-  installGetter(proto, 'validationMessage', function() {
+  installGetter(proto, 'validationMessage', function () {
     return this[internals].validationMessage;
   });
-  installGetter(proto, 'labels', function() {
+  installGetter(proto, 'labels', function () {
     return this[internals].labels;
   });
-  proto.checkValidity = function() {
+  proto.checkValidity = function () {
     return this[internals].checkValidity();
   };
-  proto.reportValidity = function() {
+  proto.reportValidity = function () {
     return this[internals].reportValidity();
   };
-  proto.setCustomValidity = function(error) {
+  proto.setCustomValidity = function (error) {
     if (error === undefined) {
       throw new TypeError('Too few arguments');
     }

third_party/blink/renderer/core/script/resources/layered_api/elements/switch/index.mjs

@@ -4,7 +4,7 @@
 
 import * as face from './face_utils.mjs';
 import * as reflection from '../internal/reflection.mjs';
-import { SwitchTrack } from './track.mjs';
+import {SwitchTrack} from './track.mjs';
 import * as style from './style.mjs';
 
 const generateStyleSheet = style.styleSheetFactory();
@@ -14,10 +14,10 @@ const STATE_ATTR = 'on';
 
 // Private property symbols
 // TODO(tkent): Use private fields.
-const _internals = Symbol();
-const _track = Symbol();
-const _rippleElement = Symbol();
-const _containerElement = Symbol();
+const _internals = Symbol('an ElementInternals field');
+const _track = Symbol('a track element field');
+const _rippleElement = Symbol('a ripple element field');
+const _containerElement = Symbol('A container element field');
 
 export class StdSwitchElement extends HTMLElement {
   // TODO(tkent): The following should be |static fooBar = value;|
@@ -43,7 +43,7 @@ export class StdSwitchElement extends HTMLElement {
   }
 
   attributeChangedCallback(attrName, oldValue, newValue) {
-    if (attrName == STATE_ATTR) {
+    if (attrName === STATE_ATTR) {
       this[_track].value = newValue !== null;
       // TODO(tkent): We should not add aria-checked attribute.
       // https://github.com/WICG/aom/issues/127
@@ -67,8 +67,8 @@ export class StdSwitchElement extends HTMLElement {
 
   // TODO(tkent): Make this private.
   _initializeDOM() {
-    let factory = this.ownerDocument;
-    let root = this.attachShadow({mode: 'closed'});
+    const factory = this.ownerDocument;
+    const root = this.attachShadow({mode: 'closed'});
     this[_containerElement] = factory.createElement('span');
     this[_containerElement].id = 'container';
     // Shadow elements should be invisible for a11y technologies.
@@ -79,19 +79,21 @@ export class StdSwitchElement extends HTMLElement {
     this[_containerElement].appendChild(this[_track].element);
     this[_track].value = this.on;
 
-    let thumbElement = this[_containerElement].appendChild(factory.createElement('span'));
+    const thumbElement =
+        this[_containerElement].appendChild(factory.createElement('span'));
     thumbElement.id = 'thumb';
     thumbElement.part.add('thumb');
 
-    this[_rippleElement] = thumbElement.appendChild(factory.createElement('span'));
+    this[_rippleElement] =
+        thumbElement.appendChild(factory.createElement('span'));
     this[_rippleElement].id = 'ripple';
 
     root.adoptedStyleSheets = [generateStyleSheet()];
   }
 
   // TODO(tkent): Make this private.
-  _onClick(event) {
-    for (let element of this[_containerElement].querySelectorAll('*')) {
+  _onClick() {
+    for (const element of this[_containerElement].querySelectorAll('*')) {
       style.markTransition(element);
     }
     this.on = !this.on;
@@ -101,7 +103,7 @@ export class StdSwitchElement extends HTMLElement {
 
   // TODO(tkent): Make this private.
   _onKeyPress(event) {
-    if (event.code == 'Space') {
+    if (event.code === 'Space') {
       // Do not scroll the page.
       event.preventDefault();
       this._onClick(event);
@@ -120,7 +122,7 @@ Object.defineProperty(StdSwitchElement.prototype, Symbol.toStringTag, {
   configurable: true,
   enumerable: false,
   value: 'StdSwitchElement',
-  writable: false
+  writable: false,
 });
 
 customElements.define('std-switch', StdSwitchElement);

third_party/blink/renderer/core/script/resources/layered_api/elements/switch/style.mjs

@@ -164,20 +164,21 @@ function setupTransitionCounter(element) {
       ++element.runningTransitions;
     }
   });
-  let handleEndOrCancel = e => {
+  function handleEndOrCancel(e) {
     // Need to check runningTransitions>0 due to superfluous transitioncancel
     // events; crbug.com/979556.
     if (e.target === element && element.runningTransitions > 0) {
       --element.runningTransitions;
     }
-  };
+  }
   element.addEventListener('transitionend', handleEndOrCancel);
   element.addEventListener('transitioncancel', handleEndOrCancel);
 }
 
 /**
- * Add '$part-transitioning' part to the element, and remove it on 'transitionend'
- * event or remove it immediately if the element has no transitions.
+ * Add '$part-transitioning' part to the element, and remove it on
+ * 'transitionend' event or remove it immediately if the element has no
+ * transitions.
  *
  * TODO(tkent): We should apply custom state.
  *
@@ -211,14 +212,14 @@ export function markTransition(element) {
     // If the element has a transition, it must start on the rendering just
     // after this rAF callback. So we check runningTransitions in the next
     // frame.
-    const removeIfNoTransitions = () => {
+    function removeIfNoTransitions() {
       // No transitions started, or all transitions were completed.
       if (element.runningTransitions === 0) {
         element.part.remove(partName);
       } else {
         window.requestAnimationFrame(removeIfNoTransitions);
       }
-    };
+    }
     window.requestAnimationFrame(removeIfNoTransitions);
   });
 }

third_party/blink/renderer/core/script/resources/layered_api/elements/switch/track.mjs

@@ -4,13 +4,12 @@
 
 // Private property symbols
 // TODO(tkent): Use private fields.
-const _value = Symbol();
-const _trackElement = Symbol();
-const _fillElement = Symbol();
-const _slotElement = Symbol();
+const _value = Symbol('A boolean track value field');
+const _trackElement = Symbol('A track element field');
+const _fillElement = Symbol('A trackFill element field');
+const _slotElement = Symbol('A slot element field');
 
 export class SwitchTrack {
-
   /**
    * @param {!Document} factory A factory for elements created for this track.
    */
@@ -30,13 +29,13 @@ export class SwitchTrack {
    * @param {Boolean} newValue
    */
   set value(newValue) {
-    let oldValue = this[_value];
+    const oldValue = this[_value];
     this[_value] = Boolean(newValue);
 
-    let bar = this[_fillElement];
+    const bar = this[_fillElement];
     if (bar) {
       bar.style.inlineSize = this[_value] ? '100%' : '0%';
-      if (oldValue != this[_value]) {
+      if (oldValue !== this[_value]) {
         this._addSlot();
       }
     }

third_party/blink/renderer/core/script/resources/layered_api/elements/toast/index.mjs

@@ -52,8 +52,8 @@ function styleSheetFactory() {
           border-color: red;
         }
       `);
-      // TODO(jacksteinberg): use offset-block-end: / offset-inline-end: over bottom: / right:
-      // when implemented https://bugs.chromium.org/p/chromium/issues/detail?id=538475
+      // TODO(jacksteinberg): use offset-block-end: / offset-inline-end: over
+      // bottom: / right: when implemented http://crbug.com/538475.
     }
     return stylesheet;
   };
@@ -108,7 +108,8 @@ export class StdToastElement extends HTMLElement {
     if (!this.hasAttribute('role')) {
       this.setAttribute('role', 'status');
     }
-    // TODO(jacksteinberg): use https://github.com/whatwg/html/pull/4658 when implemented
+    // TODO(jacksteinberg): use https://github.com/whatwg/html/pull/4658
+    // when implemented
   }
 
   get action() {
@@ -172,7 +173,8 @@ export class StdToastElement extends HTMLElement {
 
   show({duration = DEFAULT_DURATION} = {}) {
     if (duration <= 0) {
-      throw new RangeError(`Invalid Argument: duration must be greater than 0 [${duration} given]`);
+      throw new RangeError(`Invalid Argument: duration must be greater ` +
+                           `than 0 [${duration} given]`);
     }
 
     this.setAttribute('open', '');

third_party/blink/renderer/core/script/resources/layered_api/kv-storage/index.mjs

@@ -73,12 +73,13 @@ export class StorageArea {
 
   async clear() {
     if (!this.#databasePromise) {
-      // Don't try to delete, and clear the promise, while we're opening the database; wait for that
-      // first.
+      // Don't try to delete, and clear the promise, while we're opening the
+      // database; wait for that first.
       try {
         await this.#databasePromise;
       } catch {
-        // If the database failed to initialize, then that's fine, we'll still try to delete it.
+        // If the database failed to initialize, then that's fine, we'll still
+        // try to delete it.
       }
 
       this.#databasePromise = undefined;