Makes a handful of DataSources not replace the existing

chrome/browser/webui/chrome_url_data_manager_backend.cc

 // Copyright (c) 2011 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/webui/chrome_url_data_manager_backend.h"
 
 #include "base/file_util.h"
 #include "base/message_loop.h"
 #include "base/path_service.h"
 #include "base/ref_counted_memory.h"
@@ skipping 160 matching lines @@
       &ChromeURLDataManagerBackend::Factory);
   net::URLRequest::RegisterProtocolFactory(
       chrome::kChromeUIScheme,
       &ChromeURLDataManagerBackend::Factory);
 }
 
 void ChromeURLDataManagerBackend::AddDataSource(
     ChromeURLDataManager::DataSource* source) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DataSourceMap::iterator i = data_sources_.find(source->source_name());
-  if (i != data_sources_.end())
+  if (i != data_sources_.end()) {
+    if (!source->ShouldReplaceExistingSource())
+      return;
     i->second->backend_ = NULL;
+  }
   data_sources_[source->source_name()] = source;
   source->backend_ = this;
 }
 
 void ChromeURLDataManagerBackend::AddFileSource(const std::string& source_name,
                                                 const FilePath& file_path) {
   DCHECK(file_sources_.count(source_name) == 0);
   file_sources_[source_name] = file_path;
 }
 
@@ skipping 191 matching lines @@
                                            net::ERR_INVALID_URL));
   }
 }
 
 URLRequestChromeFileJob::URLRequestChromeFileJob(net::URLRequest* request,
                                                  const FilePath& path)
     : net::URLRequestFileJob(request, path) {
 }
 
 URLRequestChromeFileJob::~URLRequestChromeFileJob() {}