Hide MHTMLGenerationManager from chrome.

content/browser/download/mhtml_generation_manager.h

Index: content/browser/download/mhtml_generation_manager.h
===================================================================
--- content/browser/download/mhtml_generation_manager.h	(revision 124331)
+++ content/browser/download/mhtml_generation_manager.h	(working copy)
@@ -7,11 +7,9 @@
 
 #include <map>
 
-#include "base/memory/ref_counted.h"
+#include "base/memory/singleton.h"
 #include "base/platform_file.h"
 #include "base/process.h"
-#include "content/common/content_export.h"
-#include "content/public/browser/browser_thread.h"
 #include "ipc/ipc_platform_file.h"
 
 class FilePath;
@@ -20,12 +18,9 @@
 class WebContents;
 }
 
-class CONTENT_EXPORT MHTMLGenerationManager
-    : public base::RefCountedThreadSafe<
-          MHTMLGenerationManager, content::BrowserThread::DeleteOnUIThread> {
+class MHTMLGenerationManager {
  public:
-  MHTMLGenerationManager();
-  ~MHTMLGenerationManager();
+  static MHTMLGenerationManager* GetInstance();
 
   typedef base::Callback<void(const FilePath& /* path to the MHTML file */,
       int64 /* size of the file */)> GenerateMHTMLCallback;
@@ -42,6 +37,8 @@
   void MHTMLGenerated(int job_id, int64 mhtml_data_size);
 
  private:
+  friend struct DefaultSingletonTraits<MHTMLGenerationManager>;
+
   struct Job{
     Job();
     ~Job();
@@ -61,6 +58,9 @@
     GenerateMHTMLCallback callback;
   };
 
+  MHTMLGenerationManager();
+  ~MHTMLGenerationManager();
+
   // Called on the file thread to create |file|.
   void CreateFile(int job_id,
                   const FilePath& file,