Add a new GetInstance() method for remaining files with singleton classes under chrome/browser.

chrome/browser/upgrade_detector.h

Index: chrome/browser/upgrade_detector.h
diff --git a/chrome/browser/upgrade_detector.h b/chrome/browser/upgrade_detector.h
index 7c151285cc1e9300807778a8f586618a857ebbc9..5823608e628b318b523a7fe3e5e9b8f67b9a15c7 100644
--- a/chrome/browser/upgrade_detector.h
+++ b/chrome/browser/upgrade_detector.h
@@ -23,6 +23,9 @@ class PrefService;
 //
 class UpgradeDetector {
  public:
+  // Returns the singleton instance.
+  static UpgradeDetector* GetInstance();
+
   ~UpgradeDetector();
 
   static void RegisterPrefs(PrefService* prefs);
@@ -30,9 +33,10 @@ class UpgradeDetector {
   bool notify_upgrade() { return notify_upgrade_; }
 
  private:
-  UpgradeDetector();
   friend struct DefaultSingletonTraits<UpgradeDetector>;
 
+  UpgradeDetector();
+
   // Launches a task on the file thread to check if we have the latest version.
   void CheckForUpgrade();