Fix running default browser check/setting in UI thread on Linux....

chrome/browser/shell_integration.h

 // Copyright (c) 2006-2008 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 CHROME_BROWSER_SHELL_INTEGRATION_H__
 #define CHROME_BROWSER_SHELL_INTEGRATION_H__
 
 #include <string>
 
+#include "base/ref_counted.h"
+
+class MessageLoop;
+
 class ShellIntegration {
  public:
   // Sets Chrome as default browser (only for current user). Returns false if
   // this operation fails.
   static bool SetAsDefaultBrowser();
 
   // Returns true if this instance of Chrome is the default browser. (Defined
   // as being the handler for the http/https protocols... we don't want to
   // report false here if the user has simply chosen to open HTML files in a
   // text editor and ftp links with a FTP client).
   static bool IsDefaultBrowser();
 
   // Returns true if Firefox is likely to be the default browser for the current
   // user. This method is very fast so it can be invoked in the UI thread.
   static bool IsFirefoxDefaultBrowser();
+
+
+  // The current default browser UI state
+  enum DefaultBrowserUIState {
+    STATE_PROCESSING,
+    STATE_DEFAULT,
+    STATE_NOT_DEFAULT
+  };
+
+  class DefaultBrowserObserver {
+   public:
+    // Updates the UI state to reflect the current default browser state.
+    virtual void SetDefaultBrowserUIState(DefaultBrowserUIState state) = 0;
+  };
+  //  A helper object that handles checking if Chrome is the default browser on
+  //  Windows and also setting it as the default browser. These operations are
+  //  performed asynchronously on the file thread since registry access is
+  //  involved and this can be slow.
+  //
+  class DefaultBrowserWorker
+      : public base::RefCountedThreadSafe<DefaultBrowserWorker> {
+   public:
+    explicit DefaultBrowserWorker(DefaultBrowserObserver* observer);
+    virtual ~DefaultBrowserWorker() {};
+
+    // Checks if Chrome is the default browser.
+    void StartCheckDefaultBrowser();
+
+    // Sets Chrome as the default browser.
+    void StartSetAsDefaultBrowser();
+
+    // Called to notify the worker that the view is gone.
+    void ObserverDestroyed();
+
+   private:
+    // Functions that track the process of checking if Chrome is the default
+    // browser.  |ExecuteCheckDefaultBrowser| checks the registry on the file
+    // thread.  |CompleteCheckDefaultBrowser| notifies the view to update on the
+    // UI thread.
+    void ExecuteCheckDefaultBrowser();
+    void CompleteCheckDefaultBrowser(bool is_default);
+
+    // Functions that track the process of setting Chrome as the default
+    // browser.  |ExecuteSetAsDefaultBrowser| updates the registry on the file
+    // thread.  |CompleteSetAsDefaultBrowser| notifies the view to update on the
+    // UI thread.
+    void ExecuteSetAsDefaultBrowser();
+    void CompleteSetAsDefaultBrowser();
+
+    // Updates the UI in our associated view with the current default browser
+    // state.
+    void UpdateUI(bool is_default);
+
+    DefaultBrowserObserver* observer_;
+
+    MessageLoop* ui_loop_;
+    MessageLoop* file_loop_;
+
+    DISALLOW_COPY_AND_ASSIGN(DefaultBrowserWorker);
+  };
+
 };
 
 #endif  // CHROME_BROWSER_SHELL_INTEGRATION_H__