Bug 1786197 - Turn on ESLint rule for prefer-boolean-length-check for gfx. r=gfx-reviewers,nical

Differential Revision: https://phabricator.services.mozilla.com/D155170

.eslintrc.js

@@ -478,7 +478,6 @@ module.exports = {
     {
       files: [
         "dom/**",
-        "gfx/**",
         "image/test/browser/browser_image.js",
         "layout/**",
         "mobile/android/**",

gfx/layers/apz/test/mochitest/apz_test_utils.js

@@ -139,7 +139,7 @@ function convertTestData(testData) {
 // because those don't contain any useful data.
 function getLastNonemptyBucket(buckets) {
   for (var i = buckets.length - 1; i >= 0; --i) {
-    if (buckets[i].scrollFrames.length > 0) {
+    if (buckets[i].scrollFrames.length) {
       return buckets[i];
     }
   }
@@ -269,7 +269,7 @@ function getLastApzcTree() {
     ok(false, "expected to have compositor apz test data");
     return null;
   }
-  if (data.paints.length == 0) {
+  if (!data.paints.length) {
     ok(false, "expected to have at least one compositor paint bucket");
     return null;
   }
@@ -756,7 +756,7 @@ function getSnapshot(rect) {
 //     produces { "key": { "x": 0, "y": 0 }, "key2": [1, 2, true] }
 function getQueryArgs() {
   var args = {};
-  if (location.search.length > 0) {
+  if (location.search.length) {
     var params = location.search.substr(1).split("&");
     for (var p of params) {
       var [k, v] = p.split("=");
@@ -866,7 +866,7 @@ function hitInfoToString(hitInfo) {
       strs.push(flag);
     }
   }
-  if (strs.length == 0) {
+  if (!strs.length) {
     return "INVISIBLE";
   }
   strs.sort(function(a, b) {
@@ -1070,7 +1070,7 @@ var ApzCleanup = {
   _cleanups: [],
 
   register(func) {
-    if (this._cleanups.length == 0) {
+    if (!this._cleanups.length) {
       if (!window.isApzSubtest) {
         SimpleTest.registerCleanupFunction(this.execute.bind(this));
       } // else ApzCleanup.execute is called from runSubtestsSeriallyInFreshWindows
@@ -1079,7 +1079,7 @@ var ApzCleanup = {
   },
 
   execute() {
-    while (this._cleanups.length > 0) {
+    while (this._cleanups.length) {
       var func = this._cleanups.pop();
       try {
         func();

gfx/layers/apz/test/mochitest/helper_bug1414336.html

@@ -82,7 +82,7 @@ waitUntilApzStable().then(async () => {
   }, { once: true });
 
   target0.addEventListener("pointerup", (event) => {
-    ok(target0_events.length == 0, " should receive " + target0_events + " on target0");
+    ok(!target0_events.length, " should receive " + target0_events + " on target0");
     // Wait until the event is done processing before we end the subtest,
     // otherwise on Android the pointer events pref is flipped back to false
     // and debug builds will assert.

gfx/layers/apz/test/mochitest/helper_bug1663731_no_pointercancel_on_second_touchstart.html

@@ -51,7 +51,7 @@ async function test() {
     // end the test at the right time.
     body.addEventListener("touchend", function(e) {
       dump(`Got touchend with ${e.touches.length} touches\n`);
-      if (e.touches.length == 0) {
+      if (!e.touches.length) {
         resolve();
       }
     });

gfx/layers/apz/test/mochitest/helper_bug1682170_pointercancel_on_touchaction_pinchzoom.html

@@ -40,7 +40,7 @@ async function test() {
     // end the test at the right time.
     body.addEventListener("touchend", function(e) {
       dump(`Got touchend with ${e.touches.length} touches\n`);
-      if (e.touches.length == 0) {
+      if (!e.touches.length) {
         resolve();
       }
     });

gfx/layers/apz/test/mochitest/helper_bug982141.html

@@ -24,7 +24,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=982141
       // Get the sequence number of the last paint on the compositor side.
       // We do this before converting the APZ test data because the conversion
       // loses the order of the paints.
-      ok(compositorTestData.paints.length > 0,
+      ok(!!compositorTestData.paints.length,
                     "expected at least one paint in compositor test data");
       var lastCompositorPaint = compositorTestData.paints[compositorTestData.paints.length - 1];
       var lastCompositorPaintSeqNo = lastCompositorPaint.sequenceNumber;

gfx/layers/apz/test/mochitest/helper_interrupted_reflow.html

@@ -578,7 +578,7 @@ function getAsyncScrollOffsets(aPaintsToIgnore) {
     if (rcd == null) {
       continue;
     }
-    if (rcd.children.length > 0) {
+    if (rcd.children.length) {
       // The child may not be layerized in the first few paints, but once it is
       // layerized, it should stay layerized.
       childIsLayerized = true;
@@ -654,7 +654,7 @@ async function test() {
   var asyncScrollOffsets = getAsyncScrollOffsets(framesToSkip);
   dump("Got scroll offsets: " + JSON.stringify(asyncScrollOffsets) + "\n");
   var maxScrollParentLayerPixels = maxScroll;
-  while (asyncScrollOffsets.length > 0) {
+  while (asyncScrollOffsets.length) {
     let offset = asyncScrollOffsets.shift();
     switch (state) {
       // 0 is the initial state, the scroll offset might be zero but should