chrome: Move BrowserListObserver files out of chrome namespace.

From discussion on chromium-dev, it was decided to remove 'chrome'
namespace.
See the discussion about this that has happened in
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/pcgYLSJsii8/discussion

[email protected]

Bug: 289619
Change-Id: Ic03e825bf2a65ec1edff0bd2c9e36b2a8c24c39b
Reviewed-on: https://chromium-review.googlesource.com/821831
Commit-Queue: Chandramouli Sanchi <[email protected]>
Reviewed-by: Peter Kasting <[email protected]>
Cr-Commit-Position: refs/heads/master@{#523692}
diff --git a/chrome/browser/supervised_user/supervised_user_service.h b/chrome/browser/supervised_user/supervised_user_service.h
index 52de9289..5af40f8 100644
--- a/chrome/browser/supervised_user/supervised_user_service.h
+++ b/chrome/browser/supervised_user/supervised_user_service.h
@@ -80,7 +80,7 @@
                               public syncer::SyncTypePreferenceProvider,
 #if !defined(OS_ANDROID)
                               public syncer::SyncServiceObserver,
-                              public chrome::BrowserListObserver,
+                              public BrowserListObserver,
 #endif
                               public SupervisedUserURLFilter::Observer {
  public:
@@ -213,7 +213,7 @@
   // syncer::SyncServiceObserver implementation:
   void OnStateChanged(syncer::SyncService* sync) override;
 
-  // chrome::BrowserListObserver implementation:
+  // BrowserListObserver implementation:
   void OnBrowserSetLastActive(Browser* browser) override;
 #endif  // !defined(OS_ANDROID)