Repository: GoogleChrome/lighthouse (js)

Issue:
Support --ignore-default-chrome-flags in CLI
The command I tried is:
lighthouse <_URL_> --perf --output json --output-path=./report.json --save-assets --disable-cpu-throttling --disable-network-throttling --disable-device-emulation --verbose --chrome-flags="--load-extension=<PATH_TO_EXTENSION>"

This does not enable the extension as I can see in the logs that extensions are disabled by default:
ChromeLauncher:verbose "/usr/bin/google-chrome-stable" --disable-translate --disable-extensions ...

Pull request description:
cli: --chrome-ignore-default-flags
fixes #3946

no test b/c this is trivial and there didn't seem to be a good way to test `run.js` `getDebuggableChrome`

Patch:
diff --git a/lighthouse-cli/cli-flags.js b/lighthouse-cli/cli-flags.js
index 5588c2c98..d0ef66e9e 100644
--- a/lighthouse-cli/cli-flags.js
+++ b/lighthouse-cli/cli-flags.js
@@ -151,6 +151,7 @@ function getFlags(manualArgv) {
       .boolean([
         'disable-storage-reset', 'save-assets', 'list-all-audits',
         'list-trace-categories', 'view', 'verbose', 'quiet', 'help', 'print-config',
+        'chrome-ignore-default-flags',
       ])
       .choices('output', printer.getValidOutputOptions())
       .choices('emulated-form-factor', ['mobile', 'desktop', 'none'])
diff --git a/lighthouse-cli/run.js b/lighthouse-cli/run.js
index 8574e2342..a08f4b143 100644
--- a/lighthouse-cli/run.js
+++ b/lighthouse-cli/run.js
@@ -57,6 +57,7 @@ function parseChromeFlags(flags = '') {
 function getDebuggableChrome(flags) {
   return ChromeLauncher.launch({
     port: flags.port,
+    ignoreDefaultFlags: flags.chromeIgnoreDefaultFlags,
     chromeFlags: parseChromeFlags(flags.chromeFlags),
     logLevel: flags.logLevel,
   });
diff --git a/types/externs.d.ts b/types/externs.d.ts
index 9faa358c4..4bc8bf1ba 100644
--- a/types/externs.d.ts
+++ b/types/externs.d.ts
@@ -148,6 +148,7 @@ declare global {
      */
     export interface CliFlags extends Flags {
       _: string[];
+      chromeIgnoreDefaultFlags: boolean;
       chromeFlags: string;
       /** Output path for the generated results. */
       outputPath: string;


Test patch:
diff --git a/lighthouse-cli/test/cli/bin-test.js b/lighthouse-cli/test/cli/bin-test.js
index 3b70fd1c4..597b30357 100644
--- a/lighthouse-cli/test/cli/bin-test.js
+++ b/lighthouse-cli/test/cli/bin-test.js
@@ -45,6 +45,7 @@ beforeEach(() => {
   cliFlags = {
     _: ['http://example.com'],
     output: ['html'],
+    chromeIgnoreDefaultFlags: false,
     chromeFlags: '',
     outputPath: '',
     saveAssets: false,