Avoid disk accesses on the wrong thread in URLRequestFileJob

net/url_request/url_request_file_job.h

Index: net/url_request/url_request_file_job.h
===================================================================
--- net/url_request/url_request_file_job.h	(revision 145483)
+++ net/url_request/url_request_file_job.h	(working copy)
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/file_path.h"
+#include "base/memory/weak_ptr.h"
 #include "net/base/file_stream.h"
 #include "net/base/net_export.h"
 #include "net/http/http_byte_range.h"
@@ -53,29 +54,44 @@
   FilePath file_path_;
 
  private:
+  struct FileMetaInfo {
+    int64 file_size_;
+    std::string mime_type_;
+    bool mime_type_result_;
+    bool file_exists_;
+    bool is_directory_;

[wtc, 2012/07/13 22:38:55]

The style guide recommends that struct member names should
not have trailing underscores.

Nit: it would be nice to document the members.  All the
member names are descriptive except mime_type_result_, which
I couldn't figure out.  (It means the result/return value for
the GetMimeType function.)

+  };
+
   // Tests to see if access to |path| is allowed. If g_allow_file_access_ is
   // true, then this will return true. If the NetworkDelegate associated with
   // the |request| says it's OK, then this will also return true.
   static bool IsFileAccessAllowed(const URLRequest& request,
                                   const FilePath& path);
 
+  // Function fetching file info on a WorkerPool thread.

[wtc, 2012/07/13 22:38:55]

Nit: Function fetching => Fetches
                     or   This function fetches

Also, it may be better to call the thread "a background thread"
instead of "a WorkerPool thread" to be consistent with the
comments below.

+  static void FetchMetaInfo(const FilePath& file_path,
+                            FileMetaInfo* meta_info);
+
   // Callback after fetching file info on a background thread.
-  void DidResolve(bool exists, const base::PlatformFileInfo& file_info);
+  void DidFetchMetaInfo(const FileMetaInfo* meta_info);
 
+  // Callback after opening file on a background thread.
+  void DidOpen(int result);
+
+  // Callback after seeking to necessary position in the file which is done

[wtc, 2012/07/13 22:38:55]

Nit: change this comment to:
  // Callback after seeking to the specified position in the file on a
background thread.

+  // on a background thread.
+  void DidSeek(int64 result);
+
   // Callback after data is asynchronously read from the file.
   void DidRead(int result);
 
   FileStream stream_;
-  bool is_directory_;
+  FileMetaInfo meta_info_;
 
   HttpByteRange byte_range_;
   int64 remaining_bytes_;
 
-  // The initial file metadata is fetched on a background thread.
-  // AsyncResolver runs that task.
-  class AsyncResolver;
-  friend class AsyncResolver;
-  scoped_refptr<AsyncResolver> async_resolver_;
+  base::WeakPtrFactory<URLRequestFileJob> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequestFileJob);
 };