[testing] Correctly pass chromeBinary to karma

Karma's chrome launcher respects the CHROME_BIN env var to configure the Chrome binary to launch, and launches the system's chrome if unset, which is currently the case. We don't want to pollute the environment vars for passing settings around, so we instead subclass the Chrome launcher to use the correct default chrome.

Bug: b:333423685
Change-Id: I546d25ad84e43ca76ee45734b4c69ccffb01f63a
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/5458994
Auto-Submit: Philip Pfaffe <[email protected]>
Commit-Queue: Philip Pfaffe <[email protected]>
Reviewed-by: Simon Zünd <[email protected]>

Author: pfaffe

test/unit/karma.conf.ts

@@ -27,6 +27,20 @@ function* reporters() {
   }
 }
 
+const CustomChrome = function(this: unknown, _baseBrowserDecorator: unknown, _args: unknown, _config: unknown) {
+  require('karma-chrome-launcher')['launcher:Chrome'][1].apply(this, arguments);
+};
+
+CustomChrome.prototype = {
+  name: 'ChromeLauncher',
+
+  DEFAULT_CMD: {
+    [process.platform]: TestConfig.chromeBinary,
+  },
+  ENV_CMD: 'CHROME_BIN',
+};
+CustomChrome.$inject = ['baseBrowserDecorator', 'args', 'config'];
+
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 module.exports = function(config: any) {
   const targetDir = path.relative(SOURCE_ROOT, GEN_DIR);
@@ -60,7 +74,7 @@ module.exports = function(config: any) {
     browsers: ['BrowserWithArgs'],
     customLaunchers: {
       'BrowserWithArgs': {
-        base: 'Chrome',
+        base: CustomChrome.prototype.name,
         flags: [
           '--remote-allow-origins=*',
           `--remote-debugging-port=${REMOTE_DEBUGGING_PORT}`,
@@ -84,7 +98,7 @@ module.exports = function(config: any) {
     },
 
     plugins: [
-      require('karma-chrome-launcher'),
+      {[`launcher:${CustomChrome.prototype.name}`]: ['type', CustomChrome]},
       require('karma-mocha'),
       require('karma-mocha-reporter'),
       require('karma-chai'),