Remove stl_util's deletion function use from chrome/.

chrome/browser/printing/background_printing_manager.h

Index: chrome/browser/printing/background_printing_manager.h
diff --git a/chrome/browser/printing/background_printing_manager.h b/chrome/browser/printing/background_printing_manager.h
index 0747603b5918127c7dcc6cc37554f7a0e48f0e48..c304be0156ba75fe02c047e89b7a1453874cf307 100644
--- a/chrome/browser/printing/background_printing_manager.h
+++ b/chrome/browser/printing/background_printing_manager.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_PRINTING_BACKGROUND_PRINTING_MANAGER_H_
 
 #include <map>
+#include <memory>
 #include <set>
 
 #include "base/compiler_specific.h"
@@ -29,7 +30,6 @@ class BackgroundPrintingManager : public base::NonThreadSafe,
                                   public content::NotificationObserver {
  public:
   class Observer;
-  typedef std::map<content::WebContents*, Observer*> WebContentsObserverMap;
 
   BackgroundPrintingManager();
   ~BackgroundPrintingManager() override;
@@ -56,7 +56,8 @@ class BackgroundPrintingManager : public base::NonThreadSafe,
 
   // A map from print preview WebContentses (managed by
   // BackgroundPrintingManager) to the Observers that observe them.
-  WebContentsObserverMap printing_contents_map_;
+  std::map<content::WebContents*, std::unique_ptr<Observer>>
+      printing_contents_map_;
 
   content::NotificationRegistrar registrar_;