Fix os in JavaScript error reports

Fix 'os' metadata so that it is not hardcoded to "ChromeOS"

Bug: chromium:1121816

Change-Id: Iebdff3629d5e37b07c2ede2f298302d8f3908883
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463098
Commit-Queue: Ian Barkley-Yeung <iby@chromium.org>
Commit-Queue: Miriam Zimmerman <mutexlox@chromium.org>
Auto-Submit: Ian Barkley-Yeung <iby@chromium.org>
Reviewed-by: Miriam Zimmerman <mutexlox@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816372}

components/crash/content/browser/error_reporting/send_javascript_error_report.cc

@@ -267,8 +267,12 @@ void OnConsentCheckCompleted(
   params["browser"] = "Chrome";
   params["browser_version"] = platform.version;
   params["channel"] = platform.channel;
-  // TODO(https://crbug.com/1121816): Handle non-ChromeOS platforms.
+#if defined(OS_CHROMEOS) || BUILDFLAG(IS_LACROS)
+  // base::SysInfo::OperatingSystemName() returns "Linux" on ChromeOS devices.
   params["os"] = "ChromeOS";
+#else
+  params["os"] = base::SysInfo::OperatingSystemName();
+#endif
   params["os_version"] = platform.os_version;
   params["full_url"] = source.spec();
   params["url"] = source.path();