WebUI: Enforce one variable declaration per line with ESLint.

Per the styleguide at [1]

"Every local variable declaration declares only one variable:
declarations such as let a = 1, b = 2; are not used."

Fixing all violations (using ESLint's --fix flag), and turning on the
one-var ESLint rule to catch such violations at PRESUBMIT time in the
future.

[1] https://google.github.io/styleguide/jsguide.html#features-one-variable-per-declaration

Bug: 720034
Change-Id: I369c12ef7d456722e03fbc8f178245fa82e638c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3774879
Reviewed-by: John Lee <johntlee@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1026316}

.eslintrc.js

@@ -58,6 +58,12 @@ module.exports = {
     'quotes': ['error', 'single', {allowTemplateLiterals: true}],
     'semi': ['error', 'always'],
 
+    // https://google.github.io/styleguide/jsguide.html#features-one-variable-per-declaration
+    'one-var': ['error', {
+      let: 'never',
+      const: 'never',
+    }],
+
     // TODO(dpapad): Add more checks according to our styleguide.
   },
 

chrome/browser/resources/chromeos/accessibility/chromevox/background/braille/pan_strategy.js

@@ -130,7 +130,8 @@ export class PanStrategy {
     const buf =
         this.panStrategyWrapped_ ? this.wrappedBuffer_ : this.fixedBuffer_;
 
-    let startIndex, endIndex;
+    let startIndex;
+    let endIndex;
     if (this.panStrategyWrapped_) {
       startIndex = this.wrappedCursor_.start;
       endIndex = this.wrappedCursor_.end;
@@ -353,7 +354,8 @@ export class PanStrategy {
     const contentLength =
         this.panStrategyWrapped_ ? this.wrappedLineCount : this.fixedLineCount;
     if (this.viewPort_.firstRow > 0) {
-      let newStart, newEnd;
+      let newStart;
+      let newEnd;
       if (this.viewPort_.firstRow < this.displaySize_.rows) {
         newStart = 0;
         newEnd = Math.min(this.displaySize_.rows, contentLength);

chrome/browser/resources/chromeos/accessibility/chromevox/background/command_handler.js

@@ -1136,7 +1136,8 @@ export class CommandHandler extends CommandHandlerInterface {
         }
 
         // Get word start and end indices.
-        let wordStarts, wordEnds;
+        let wordStarts;
+        let wordEnds;
         if (node.role === RoleType.INLINE_TEXT_BOX) {
           wordStarts = node.wordStarts;
           wordEnds = node.wordEnds;

chrome/browser/resources/chromeos/accessibility/chromevox/background/output/output.js

@@ -554,7 +554,8 @@ export class Output {
     if (this.brailleBuffer_.length) {
       const buff = this.mergeBraille_(this.brailleBuffer_);
       const selSpan = buff.getSpanInstanceOf(OutputSelectionSpan);
-      let startIndex = -1, endIndex = -1;
+      let startIndex = -1;
+      let endIndex = -1;
       if (selSpan) {
         const valueStart = buff.getSpanStart(selSpan);
         const valueEnd = buff.getSpanEnd(selSpan);

chrome/browser/resources/chromeos/accessibility/chromevox/background/tts_background_test.js

@@ -155,7 +155,8 @@ TEST_F('ChromeVoxTtsBackgroundTest', 'UpdateVoice', function() {
 TEST_F(
     'ChromeVoxTtsBackgroundTest', 'DISABLED_EmptyStringCallsCallbacks',
     function() {
-      let startCalls = 0, endCalls = 0;
+      let startCalls = 0;
+      let endCalls = 0;
       assertCallsCallbacks = (text, speakCalls) => {
         tts.speak(text, QueueMode.QUEUE, {
           startCallback() {

chrome/browser/resources/chromeos/accessibility/chromevox/panel/panel.js

@@ -641,7 +641,8 @@ export class Panel extends PanelInterface {
       Panel.brailleTableElement2_.deleteRow(0);
     }
 
-    let row1, row2;
+    let row1;
+    let row2;
     // Number of rows already written.
     rowCount = 0;
     // Number of cells already written in this row.

chrome/browser/resources/chromeos/accessibility/chromevox/testing/mock_feedback.js

@@ -523,7 +523,8 @@ MockFeedback = class {
      * @private
      */
     static matchAndConsume_(text, props, pending) {
-      let i, candidate;
+      let i;
+      let candidate;
       for (i = 0; candidate = pending[i]; ++i) {
         let candidateText = candidate.text;
         if (typeof (candidateText) !== 'string') {

chrome/browser/resources/chromeos/accessibility/common/automation_predicate.js

@@ -638,7 +638,8 @@ AutomationPredicate = class {
     const dir = opts.dir || Dir.FORWARD;
 
     // Compute the row/col index defaulting to 0.
-    let rowIndex = 0, colIndex = 0;
+    let rowIndex = 0;
+    let colIndex = 0;
     let tableNode = start;
     while (tableNode) {
       if (AutomationPredicate.table(tableNode)) {

chrome/browser/resources/chromeos/accessibility/common/automation_util_test.js

@@ -103,7 +103,8 @@ AX_TEST_F(
     'AccessibilityExtensionAutomationUtilE2ETest', 'GetUniqueAncestors',
     async function() {
       const root = await this.runWithLoadedTree(this.basicDoc());
-      let leftmost = root, rightmost = root;
+      let leftmost = root;
+      let rightmost = root;
       while (leftmost.firstChild) {
         leftmost = leftmost.firstChild;
       }
@@ -142,7 +143,8 @@ AX_TEST_F(
     'AccessibilityExtensionAutomationUtilE2ETest', 'GetDirection',
     async function() {
       const root = await this.runWithLoadedTree(this.basicDoc());
-      let left = root, right = root;
+      let left = root;
+      let right = root;
 
       // Same node.
       assertEquals(Dir.FORWARD, AutomationUtil.getDirection(left, right));

chrome/browser/resources/chromeos/accessibility/common/cursors/cursor.js

@@ -324,15 +324,17 @@ export class Cursor {
 
         switch (movement) {
           case CursorMovement.BOUND: {
-            let wordStarts, wordEnds;
+            let wordStarts;
+            let wordEnds;
             if (newNode.role === RoleType.INLINE_TEXT_BOX) {
               wordStarts = newNode.wordStarts;
               wordEnds = newNode.wordEnds;
             } else {
               wordStarts = newNode.nonInlineTextWordStarts;
               wordEnds = newNode.nonInlineTextWordEnds;
             }
-            let start, end;
+            let start;
+            let end;
             for (let i = 0; i < wordStarts.length; i++) {
               if (newIndex >= wordStarts[i] && newIndex < wordEnds[i]) {
                 start = wordStarts[i];
@@ -351,7 +353,8 @@ export class Cursor {
             }
           // fallthrough
           case CursorMovement.DIRECTIONAL: {
-            let wordStarts, wordEnds;
+            let wordStarts;
+            let wordEnds;
             let start;
             if (newNode.role === RoleType.INLINE_TEXT_BOX) {
               wordStarts = newNode.wordStarts;
@@ -520,7 +523,8 @@ export class Cursor {
           break;
         }
 
-        let targetLine, targetIndex = 0;
+        let targetLine;
+        let targetIndex = 0;
         for (let i = 0, line, cur = 0; line = lines[i]; i++) {
           const lineLength = line.name ? line.name.length : 1;
           cur += lineLength;

chrome/browser/resources/chromeos/accessibility/common/cursors/range.js

@@ -214,7 +214,8 @@ export class CursorRange {
    * Select the text contained within this range.
    */
   select() {
-    let start = this.start_, end = this.end_;
+    let start = this.start_;
+    let end = this.end_;
     if (this.start.compare(this.end) === constants.Dir.BACKWARD) {
       start = this.end;
       end = this.start;

chrome/browser/resources/chromeos/accessibility/common/rect_util.js

@@ -143,7 +143,10 @@ export const RectUtil = {
       return RectUtil.ZERO_RECT;
     }
 
-    let above, below, toTheLeft, toTheRight;
+    let above;
+    let below;
+    let toTheLeft;
+    let toTheRight;
 
     if (outer.top < subtrahend.top) {
       above = {

chrome/browser/resources/chromeos/accessibility/select_to_speak/node_navigation_utils.js

@@ -275,7 +275,8 @@ export class NodeNavigationUtils {
    */
   static getNodesForNextSentence(
       currentNodeGroup, currentCharIndex, direction, pred) {
-    let nodes = [], offset;
+    let nodes = [];
+    let offset;
     if (!currentNodeGroup) {
       return {nodes, offset};
     }

chrome/browser/resources/chromeos/accessibility/select_to_speak/node_navigation_utils_unittest.js

@@ -644,7 +644,8 @@ AX_TEST_F(
       // Second paragraph has another two sentences.
       assertEquals(nodeGroupForParagraph2.text, 'Line 3. Line 4. ');
 
-      let nodes, offset;
+      let nodes;
+      let offset;
       // Navigating forward from the first sentence returns the second sentence.
       ({nodes, offset} = NodeNavigationUtils.getNodesForNextSentence(
            nodeGroupForParagraph1, 0 /* currentCharIndex */,
@@ -793,7 +794,9 @@ AX_TEST_F(
           nodeGroup.text,
           'Line 1. This sentence is chopped. Another chopped sentence. ');
 
-      let nodes, offset, result;
+      let nodes;
+      let offset;
+      let result;
       // Navigating forward from the first word returns the content starting
       // from the second sentence.
       ({nodes, offset} = NodeNavigationUtils.getNodesForNextSentence(

chrome/browser/resources/chromeos/accessibility/select_to_speak/node_utils.js

@@ -495,7 +495,8 @@ export class NodeUtils {
    * @return {!NodeUtils.Position}
    */
   static getPositionFromNodeGroup(nodeGroup, charIndex, fallbackToEnd) {
-    let node, offset;
+    let node;
+    let offset;
     if (charIndex !== undefined) {
       ({node, offset} = ParagraphUtils.findNodeFromNodeGroupByCharIndex(
            nodeGroup, charIndex));

chrome/browser/resources/chromeos/accessibility/select_to_speak/paragraph_utils_unittest.js

@@ -603,7 +603,9 @@ AX_TEST_F(
       const thirdStatic = 'No child sentence.';
       const thirdSentence = thirdStatic + ' ';
 
-      let nodeGroup, startIndexInGroup, endIndexInGroup;
+      let nodeGroup;
+      let startIndexInGroup;
+      let endIndexInGroup;
       ({nodeGroup, startIndexInGroup, endIndexInGroup} =
            ParagraphUtils.buildSingleNodeGroupWithOffset(nodes));
       assertEquals(

chrome/browser/resources/chromeos/accessibility/switch_access/saatlite/compiler/parser.js

@@ -3536,7 +3536,9 @@ var parser = (function() {
   }();
   parser.lexer = lexer;
 
-  let page, point, objectToMatch;
+  let page;
+  let point;
+  let objectToMatch;
 
   let indent = '';
   const increaseIndent = () => indent = indent + '  ';

chrome/browser/resources/chromeos/internet_detail_dialog/internet_detail_dialog.js

@@ -130,7 +130,8 @@ Polymer({
   attached() {
     this.browserProxy_ = InternetDetailDialogBrowserProxyImpl.getInstance();
     const dialogArgs = this.browserProxy_.getDialogArguments();
-    let type, name;
+    let type;
+    let name;
     if (dialogArgs) {
       const args = JSON.parse(dialogArgs);
       this.guid = args.guid || '';

chrome/browser/resources/hangout_services/thunk.js

@@ -277,7 +277,8 @@ function onProcessCpu(port) {
       return;
     }
 
-    let browserProcessCpu, gpuProcessCpu;
+    let browserProcessCpu;
+    let gpuProcessCpu;
     for (const pid in processes) {
       const process = processes[pid];
       if (process.type === 'browser') {

chrome/browser/resources/new_tab_page/modules/cart/module.ts

@@ -343,7 +343,8 @@ export class ChromeCartModuleElement extends I18nMixin
    */
   private onLeftScrollClick_() {
     const carts = this.$.cartCarousel.querySelectorAll('.cart-container');
-    let visibleRange = 0, firstVisibleIndex = 0;
+    let visibleRange = 0;
+    let firstVisibleIndex = 0;
     for (let i = carts.length - 1; i >= 0; i--) {
       if (this.getVisibilityForIndex_(i)) {
         visibleRange += 1;

chrome/browser/resources/settings/chromeos/device_page/layout_behavior.js

@@ -323,7 +323,8 @@ export const LayoutBehavior = {
    * @private
    */
   calculateBounds_(id, width, height) {
-    let left, top;
+    let left;
+    let top;
     const layout = this.displayLayoutMap_.get(id);
     if (this.mirroring || !layout || !layout.parentId) {
       left = -width / 2;
@@ -394,7 +395,8 @@ export const LayoutBehavior = {
       if (x >= left && x < left + width && y >= top && y < top + height) {
         return otherId;
       }  // point is inside rect
-      let dx, dy;
+      let dx;
+      let dy;
       if (x < left) {
         dx = left - x;
       } else if (x > left + width) {
@@ -654,7 +656,9 @@ export const LayoutBehavior = {
 
     // Offset is calculated from top or left edge.
     const parentBounds = this.getCalculatedDisplayBounds(layout.parentId);
-    let offset, minOffset, maxOffset;
+    let offset;
+    let minOffset;
+    let maxOffset;
     if (position === chrome.system.display.LayoutPosition.LEFT ||
         position === chrome.system.display.LayoutPosition.RIGHT) {
       offset = bounds.top - parentBounds.top;

chrome/test/data/webui/bookmarks/extension_api_test.js

@@ -9,9 +9,20 @@ test('bookmarkManagerPrivate', async () => {
   const bookmarkManager = chrome.bookmarkManagerPrivate;
   const {pass, fail, runTests} = simulateChromeExtensionAPITest();
 
-  let fooNode, fooNode2, barNode, gooNode, count, emptyFolder, emptyFolder2;
-  let folder, nodeA, nodeB;
-  let childFolder, grandChildFolder, childNodeA, childNodeB;
+  let fooNode;
+  let fooNode2;
+  let barNode;
+  let gooNode;
+  let count;
+  let emptyFolder;
+  let emptyFolder2;
+  let folder;
+  let nodeA;
+  let nodeB;
+  let childFolder;
+  let grandChildFolder;
+  let childNodeA;
+  let childNodeB;
 
   function doCopy() {
     bookmarkManager.copy.apply(null, arguments);

chrome/test/data/webui/side_panel/bookmarks/bookmarks_drag_manager_test.ts

@@ -101,7 +101,10 @@ suite('SidePanelBookmarkDragManagerTest', () => {
   });
 
   test('DragStartCallsAPI', () => {
-    let calledIds, calledIndex, calledX, calledY;
+    let calledIds;
+    let calledIndex;
+    let calledX;
+    let calledY;
     let calledTouch = false;
     chrome.bookmarkManagerPrivate.startDrag =
         (ids: string[], index: number, touch: boolean, x: number,
@@ -189,7 +192,8 @@ suite('SidePanelBookmarkDragManagerTest', () => {
   });
 
   test('DropsIntoFolder', () => {
-    let calledId, calledIndex;
+    let calledId;
+    let calledIndex;
     chrome.bookmarkManagerPrivate.startDrag = () => {};
     chrome.bookmarkManagerPrivate.drop = (id, index) => {
       calledId = id;
@@ -217,7 +221,8 @@ suite('SidePanelBookmarkDragManagerTest', () => {
   });
 
   test('DropsBookmarksToReorder', () => {
-    let calledId, calledIndex;
+    let calledId;
+    let calledIndex;
     chrome.bookmarkManagerPrivate.startDrag = () => {};
     chrome.bookmarkManagerPrivate.drop = (id, index) => {
       calledId = id;

ui/file_manager/file_manager/foreground/js/navigation_list_model.js

@@ -616,7 +616,8 @@ export class NavigationListModel extends EventTarget {
       this.navigationItems_.push(shortcut);
     }
 
-    let myFilesEntry, myFilesModel;
+    let myFilesEntry;
+    let myFilesModel;
     if (!this.myFilesModel_) {
       // When MyFilesVolume is enabled we use the Downloads volume to be the
       // MyFiles volume.

ui/file_manager/image_loader/piex_loader.js

@@ -512,10 +512,14 @@ class ImageBuffer {
     bitmap.setUint32(62, /* BlueMask */ 0, true);
     bitmap.setUint32(66, /* AlphaMask */ 0, true);
 
-    let rx = 0, ry = 0;
-    let gx = 0, gy = 0;
-    let bx = 0, by = 0;
-    let zz = 0, gg = 0;
+    let rx = 0;
+    let ry = 0;
+    let gx = 0;
+    let gy = 0;
+    let bx = 0;
+    let by = 0;
+    let zz = 0;
+    let gg = 0;
 
     if (thumbnail.colorSpace !== 'adobeRgb') {
       bitmap.setUint8(70, 's'.charCodeAt(0));