MD History: update (instead of re-create) data sources on sign in change

content/public/browser/web_ui_data_source.h

 // Copyright (c) 2013 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_WEB_UI_DATA_SOURCE_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_UI_DATA_SOURCE_H_
 
 #include <stdint.h>
 

[Charlie Reis, 2016/11/16 18:38:46]

nit: No blank line?

+#include <memory>
+
 #include "base/callback.h"
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
 
 namespace base {
 class DictionaryValue;
 class RefCountedMemory;
 }
 
 namespace content {
 class BrowserContext;
 
 // A data source that can help with implementing the common operations needed by
 // WebUI pages.
 class WebUIDataSource {
  public:
   virtual ~WebUIDataSource() {}
 
   CONTENT_EXPORT static WebUIDataSource* Create(const std::string& source_name);
 
-  // Adds a WebUI data source to |browser_context|.
+  // Adds a WebUI data source to |browser_context|. TODO(dbeam): update this API
+  // to take a std::unique_ptr instead to make it clear that |source| can be
+  // destroyed and references should not be kept by callers. Use |Update()|
+  // if you need to change an existing data source.
   CONTENT_EXPORT static void Add(BrowserContext* browser_context,
                                  WebUIDataSource* source);
 
+  CONTENT_EXPORT static void Update(

[Charlie Reis, 2016/11/16 18:38:46]

Please include comments for all methods in the public interface.  (It's probably
worth also explaining why some cases should use Update rather than Add, given
the bug it's fixing.)

+      BrowserContext* browser_context,
+      const std::string& source_name,
+      std::unique_ptr<base::DictionaryValue> update);
+
   // Adds a string keyed to its name to our dictionary.
   virtual void AddString(const std::string& name,
                          const base::string16& value) = 0;
 
   // Adds a string keyed to its name to our dictionary.
   virtual void AddString(const std::string& name, const std::string& value) = 0;
 
   // Adds a localized string with resource |ids| keyed to its name to our
   // dictionary.
   virtual void AddLocalizedString(const std::string& name, int ids) = 0;
@@ skipping 50 matching lines @@
   virtual void DisableDenyXFrameOptions() = 0;
 
   // Tells the loading code that resources are gzipped on disk. TODO(dbeam):
   // write a streaming $i18n{} replacer and remove the "DisableI18n" part.
   virtual void DisableI18nAndUseGzipForAllPaths() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_UI_DATA_SOURCE_H_