Update extensions with Drag-and-Drop in extension settings page.

chrome/browser/extensions/crx_installer.h

Index: chrome/browser/extensions/crx_installer.h
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index 90ad00134ae94916ac6c0eaa4f5811fb1a407d1d..0f49f3bdb0c76b6d7e308dce685d4a6e70ae3ce8 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -247,8 +247,13 @@ class CrxInstaller
   // Deletes temporary directory and crx file if needed.
   void CleanupTempFiles();
 
-  // Creates sequenced task runner for extension install file I/O operations.
-  scoped_refptr<base::SequencedTaskRunner> CreateSequencedTaskRunner();
+  // Checks whether the current installation is initiated by the user from
+  // the extension settings page to update an existing extension or app.
+  void CheckUpdateFromSettingsPage();
+
+  // Show re-enable prompt if the update is initiated from the settings page
+  // and needs additional permissions.
+  void ConfirmReEnable();
 
   // The file we're installing.
   base::FilePath source_file_;
@@ -393,6 +398,10 @@ class CrxInstaller
   // Used to show the install dialog.
   ExtensionInstallPrompt::ShowDialogCallback show_dialog_callback_;
 
+  // Whether the update is initiated by the user from the extension settings
+  // page.
+  bool update_from_settings_page_;
+
   DISALLOW_COPY_AND_ASSIGN(CrxInstaller);
 };