Remove the inactive user toast and supporting experiment infrastructure

This has not been used in years and can no longer be triggered
server-side.

Bug: 1484351
Low-Coverage-Reason: LARGE_SCALE_REFACTOR
Change-Id: I43fc2f9d1189e6e5b7908649083df5624fa1e117
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4879014
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Greg Thompson <[email protected]>
Auto-Submit: Peter Kasting <[email protected]>
Commit-Queue: Avi Drissman <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1205320}
diff --git a/chrome/browser/chrome_process_singleton.h b/chrome/browser/chrome_process_singleton.h
index 357590f..3f3d55f 100644
--- a/chrome/browser/chrome_process_singleton.h
+++ b/chrome/browser/chrome_process_singleton.h
@@ -8,21 +8,13 @@
 #include "base/files/file_path.h"
 #include "base/functional/callback.h"
 #include "chrome/browser/process_singleton.h"
-#include "chrome/browser/process_singleton_modal_dialog_lock.h"
 #include "chrome/browser/process_singleton_startup_lock.h"
 
-// Composes a basic ProcessSingleton with ProcessSingletonStartupLock and
-// ProcessSingletonModalDialogLock.
+// Composes a `ProcessSingleton` with a `ProcessSingletonStartupLock`.
 //
-// Notifications from ProcessSingleton will first close a modal dialog if
-// active. Otherwise, until |Unlock()| is called, they will be queued up. Once
-// unlocked, notifications will be passed to the client-supplied
-// NotificationCallback; which is passed as an argument by |Unlock()|.
-//
-// The client must ensure that SetModalDialogNotificationHandler is called
-// appropriately when dialogs are displayed or dismissed during startup. If a
-// dialog is active, it is closed (via the provided handler) and then the
-// notification is processed as normal.
+// Notifications from `ProcessSingleton` will be queued up until `Unlock()` is
+// called. Once unlocked, notifications will be passed to the
+// `NotificationCallback` passed to `Unlock()`.
 class ChromeProcessSingleton {
  public:
   explicit ChromeProcessSingleton(const base::FilePath& user_data_dir);
@@ -48,11 +40,6 @@
   // Clear any lock state during shutdown.
   void Cleanup();
 
-  // Receives a callback to be run to close the active modal dialog, or an empty
-  // closure if the active dialog is dismissed.
-  void SetModalDialogNotificationHandler(
-      base::RepeatingClosure notification_handler);
-
   // Executes previously queued command-line invocations and allows future
   // invocations to be executed immediately.
   // This only has an effect the first time it is called.
@@ -87,7 +74,6 @@
   // Notifications passing through both locks are finally delivered to our
   // client.
   ProcessSingletonStartupLock startup_lock_;
-  ProcessSingletonModalDialogLock modal_dialog_lock_;
 
   // The basic ProcessSingleton
   ProcessSingleton process_singleton_;