chrome: Cleanup class/struct forward declarations

chrome/browser/android/background_sync_launcher_android.h

Index: chrome/browser/android/background_sync_launcher_android.h
diff --git a/chrome/browser/android/background_sync_launcher_android.h b/chrome/browser/android/background_sync_launcher_android.h
index 99af8663a7a7dc3d2450cb9e8405830e823006b2..2ce1522bed8952c7329dbf846eaf2fdbecab152e 100644
--- a/chrome/browser/android/background_sync_launcher_android.h
+++ b/chrome/browser/android/background_sync_launcher_android.h
@@ -13,12 +13,6 @@
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 
-namespace content {
-
-class BackgroundSyncManager;
-
-}
-
 // The BackgroundSyncLauncherAndroid singleton owns the Java
 // BackgroundSyncLauncher object and is used to register interest in starting
 // the browser the next time the device goes online. This class runs on the UI