Disable Glic in response to policy

In https://crrev.com/c/6142513 we added an enterprise policy to allow
admins to disable Glic. That CL added the policy and mapped it to a
pref but didn't connect the pref to any behavior.

This CL implements the pref's behavior by disabling Glic in any profile
that's disabled by this policy. It also changes the background mode
manager to only enter background mode if there's any profile loaded that
doesn't have a disabling policy.

Bug: 382722218
Change-Id: I06b947bb363791c407d39524fed65d819e82a4e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6141955
Reviewed-by: Erik Chen <[email protected]>
Reviewed-by: Carlos Knippschild <[email protected]>
Commit-Queue: David Bokan <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1404912}
diff --git a/chrome/browser/global_features.h b/chrome/browser/global_features.h
index 7a7ee16..068eb0a 100644
--- a/chrome/browser/global_features.h
+++ b/chrome/browser/global_features.h
@@ -45,6 +45,9 @@
   // Called exactly once to initialize features.
   void Init();
 
+  // Called exactly once when the browser starts to shutdown.
+  void Shutdown();
+
   // Public accessors for features, e.g.
   // FooFeature* foo_feature() { return foo_feature_.get(); }