Cleanup: Remove unneeded forward declarations from various chrome/browser subdirectories.

chrome/browser/webdata/autocomplete_syncable_service.h

Index: chrome/browser/webdata/autocomplete_syncable_service.h
===================================================================
--- chrome/browser/webdata/autocomplete_syncable_service.h	(revision 109953)
+++ chrome/browser/webdata/autocomplete_syncable_service.h	(working copy)
@@ -7,6 +7,7 @@
 
 #include <map>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
@@ -24,10 +25,6 @@
 
 class ProfileSyncServiceAutofillTest;
 
-namespace browser_sync {
-class UnrecoverableErrorHandler;
-}
-
 namespace sync_pb {
 class AutofillSpecifics;
 }