Fix assumption: HttpTransactionFactory::GetCache() may return NULL.

content/browser/web_contents/web_contents_impl.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 "content/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
@@ skipping 134 matching lines @@
                                        url,
                                        is_favicon,
                                        max_bitmap_size));
   return g_next_image_download_id;
 }
 
 void NotifyCacheOnIO(
     scoped_refptr<net::URLRequestContextGetter> request_context,
     const GURL& url,
     const std::string& http_method) {
-  request_context->GetURLRequestContext()->http_transaction_factory()->
-      GetCache()->OnExternalCacheHit(url, http_method);
+  net::HttpCache* cache = request_context->GetURLRequestContext()->
+      http_transaction_factory()->GetCache();
+  if (cache)
+    cache->OnExternalCacheHit(url, http_method);
 }
 
 // Helper function for retrieving all the sites in a frame tree.
 bool CollectSites(BrowserContext* context,
                   std::set<GURL>* sites,
                   FrameTreeNode* node) {
   sites->insert(SiteInstance::GetSiteForURL(context, node->current_url()));
   return true;
 }
 
@@ skipping 4368 matching lines @@
   node->render_manager()->ResumeResponseDeferredAtStart();
 }
 
 void WebContentsImpl::SetForceDisableOverscrollContent(bool force_disable) {
   force_disable_overscroll_content_ = force_disable;
   if (view_)
     view_->SetOverscrollControllerEnabled(CanOverscrollContent());
 }
 
 }  // namespace content