Created an interface for DownloadFile, for use in unit tests.

content/browser/download/save_file.h

Index: content/browser/download/save_file.h
diff --git a/content/browser/download/save_file.h b/content/browser/download/save_file.h
index e7faaeb607fea6a278653ae3f5bc3aecb4dbb5c0..bfbe901b6f7c358277e619e1d8cbaf9e4178d13e 100644
--- a/content/browser/download/save_file.h
+++ b/content/browser/download/save_file.h
@@ -19,11 +19,35 @@
 // the saving job is 'in progress': once the saving job has been completed or
 // canceled, the SaveFile is destroyed. One SaveFile object represents one item
 // in a save session.
-class SaveFile : public BaseFile {
+class SaveFile {
  public:
   explicit SaveFile(const SaveFileCreateInfo* info);
   virtual ~SaveFile();
 
+  // BaseFile delegated functions.

[Randy Smith (Not in Mondays), 2011/11/10 21:58:43]

nit: As I understand chrome custom (and I think there are some arguments
stronger than customer, though I don't remember them) pretty much anything that
isn't in the "simple accessor" category should be in a .cc file.

[ahendrickson, 2011/11/13 00:50:21]

Done.

+  net::Error Initialize(bool calculate_hash) {
+    return file_.Initialize(calculate_hash);
+  }
+  net::Error AppendDataToFile(const char* data, size_t data_len) {
+    return file_.AppendDataToFile(data, data_len);
+  }
+  net::Error Rename(const FilePath& full_path) {
+    return file_.Rename(full_path);
+  }
+  void Detach() { file_.Detach(); }
+  void Cancel() { file_.Cancel(); }
+  void Finish() { file_.Finish(); }
+  void AnnotateWithSourceInformation() {
+    file_.AnnotateWithSourceInformation();
+  }
+  FilePath full_path() const { return file_.full_path(); }
+  bool in_progress() const { return file_.in_progress(); }
+  int64 bytes_so_far() const { return file_.bytes_so_far(); }
+  bool GetSha256Hash(std::string* hash) {
+    return file_.GetSha256Hash(hash);
+  }
+  std::string DebugString() const { return file_.DebugString(); }
+
   // Accessors.
   int save_id() const { return info_->save_id; }
   int render_process_id() const { return info_->render_process_id; }
@@ -34,6 +58,7 @@ class SaveFile : public BaseFile {
   }
 
  private:
+  BaseFile file_;
   scoped_ptr<const SaveFileCreateInfo> info_;
 
   DISALLOW_COPY_AND_ASSIGN(SaveFile);