[Sync] Remove unneeded 'using syncer::' lines and 'syncer::' scopings

sync/internal_api/public/util/weak_handle.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Weak handles provides a way to refer to weak pointers from another
 // thread.  This is useful because it is not safe to reference a weak
 // pointer from a thread other than the thread on which it was
 // created.
 //
 // Weak handles can be passed across threads, so for example, you can
@@ skipping 267 matching lines @@
 
   // Creates an initialized WeakHandle from |ptr|.
   explicit WeakHandle(const base::WeakPtr<T>& ptr)
       : core_(new internal::WeakHandleCore<T>(ptr)) {}
 
   // Allow conversion from WeakHandle<U> to WeakHandle<T> if U is
   // convertible to T, but we *must* be on |other|'s owner thread.
   // Note that this doesn't override the regular copy constructor, so
   // that one can be called on any thread.
   template <typename U>
-  WeakHandle(const syncer::WeakHandle<U>& other)  // NOLINT
+  WeakHandle(const WeakHandle<U>& other)  // NOLINT
       : core_(
           other.IsInitialized() ?
           new internal::WeakHandleCore<T>(other.Get()) :
           NULL) {}
 
   // Returns true iff this WeakHandle is initialized.  Note that being
   // initialized isn't a guarantee that the underlying object is still
   // alive.
   bool IsInitialized() const {
     return core_.get() != NULL;
@@ skipping 70 matching lines @@
 
 // Makes a WeakHandle from a WeakPtr.
 template <typename T>
 WeakHandle<T> MakeWeakHandle(const base::WeakPtr<T>& ptr) {
   return WeakHandle<T>(ptr);
 }
 
 }  // namespace syncer
 
 #endif  // SYNC_UTIL_WEAK_HANDLE_H_