[browser_launcher] Add --test-type flag (#2311)

Closes #2300

Some flags like disabling `TimerThrottlingForBackgroundTabs` cause
warnings when launching chrome because it is not recommended for use
during general browsing. Suppress these types of warnings with the
`--test-type` flag which indicates to chrome that this is a dev focused
workflow where such flags are expected.

Author: natebosch

pkgs/browser_launcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.2.0-wip
+
+- Add `--test-type` flag when launching chrome to prevent some warnings.
+
 ## 1.1.3
 
 - Move to `dart-lang/tools` monorepo.

pkgs/browser_launcher/lib/src/chrome.dart

@@ -118,6 +118,9 @@ class Chrome {
       // credentials. This uses a mock keychain to avoid that dialog from
       // blocking.
       '--use-mock-keychain',
+      // Prevent warnings for using flags that are not recommended for general
+      // browsing but are applicable for use in dev-focused workflows.
+      '--test-type',
     ];
     if (headless) {
       args.add('--headless');

pkgs/browser_launcher/pubspec.yaml

@@ -1,5 +1,5 @@
 name: browser_launcher
-version: 1.1.3
+version: 1.2.0-wip
 description: Provides a standardized way to launch web browsers for testing and tools.
 repository: https://github.com/dart-lang/tools/tree/main/pkgs/browser_launcher
 issue_tracker: https://github.com/dart-lang/tools/issues?q=is%3Aissue+is%3Aopen+label%3Apackage%3Abrowser_launcher