Fix link error when safe browsing is disabled.

chrome/browser/memory_purger.cc

 // 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.
 
 #include "chrome/browser/memory_purger.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/threading/thread.h"
@@ skipping 49 matching lines @@
 }
 
 void PurgeMemoryIOHelper::PurgeMemoryOnIOThread() {
   // Ask ProxyServices to purge any memory they can (generally garbage in the
   // wrapped ProxyResolver's JS engine).
   for (size_t i = 0; i < request_context_getters_.size(); ++i) {
     request_context_getters_[i]->GetURLRequestContext()->proxy_service()->
         PurgeMemory();
   }
 
+#if defined(ENABLE_SAFE_BROWSING)
   safe_browsing_service_->PurgeMemory();
+#endif
 }
 
 // -----------------------------------------------------------------------------
 
 // static
 void MemoryPurger::PurgeAll() {
   PurgeBrowser();
   PurgeRenderers();
 
   // TODO(pkasting):
@@ skipping 65 matching lines @@
           content::RenderProcessHost::AllHostsIterator());
        !i.IsAtEnd(); i.Advance())
     PurgeRendererForHost(i.GetCurrentValue());
 }
 
 // static
 void MemoryPurger::PurgeRendererForHost(content::RenderProcessHost* host) {
   // Direct the renderer to free everything it can.
   host->Send(new ChromeViewMsg_PurgeMemory());
 }