system-web-apps: update comments about internal_name

SWA internal name is used for metrics and tast tests. This CL updates
the comment to reflect this.

Change-Id: I8f6fe694996c6a1ed186a8afb54578b2564981eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2386903
Commit-Queue: Jiewei Qian  <qjw@chromium.org>
Auto-Submit: Jiewei Qian  <qjw@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804677}

chrome/browser/web_applications/system_web_app_manager.h

@@ -78,8 +78,9 @@ struct SystemAppInfo {
   SystemAppInfo(const SystemAppInfo& other);
   ~SystemAppInfo();
 
-  // A developer-friendly name for reporting metrics. Should follow UMA naming
-  // conventions.
+  // A developer-friendly name for, among other things, reporting metrics and
+  // interacting with tast tests. It should follow PascalCase convention. It
+  // shouldn't be changed afterwards.
   std::string internal_name;
 
   // The URL that the System App will be installed from.