Added member data to classes to support download resumption.

content/browser/download/base_file.h

Index: content/browser/download/base_file.h
diff --git a/content/browser/download/base_file.h b/content/browser/download/base_file.h
index 7076ef146678274ecb28fa62c4a57f5df583431b..e4ac541746d1a7cc8dbe25153d6c8a59ec981411 100644
--- a/content/browser/download/base_file.h
+++ b/content/browser/download/base_file.h
@@ -63,7 +63,17 @@ class CONTENT_EXPORT BaseFile {
   bool in_progress() const { return file_stream_ != NULL; }
   int64 bytes_so_far() const { return bytes_so_far_; }
 
-  // Set |hash| with sha256 digest for the file.
+  // Copies the current sha256 digest for the file into |hash|.  May be partial.
+  // Used to save the hash in the case of download resumption.
+  // Returns true on success, false on failure.
+  bool GetPartialSha256Hash(std::string* hash);

[Randy Smith (Not in Mondays), 2011/10/31 18:46:43]

I'd like to look at combining the concepts of partial and total hash; just
provide "GetHash" methods, and whether they're partial or total depends on
whether the object on which they're being executed are partial or total.  

[ahendrickson, 2011/11/13 21:15:20]

Done.

+
+  // Sets the sha256 digest for the file from |hash|.
+  // Used to restore the hash in the case of download resumption.
+  // Returns true on success, false on failure.
+  bool SetPartialSha256Hash(const std::string& hash);

[Randy Smith (Not in Mondays), 2011/10/31 18:46:43]

Hmmm.  This feels like something that's relevant only on creation, and hence
should be part of the constructor.  (I could imagine--not sure it's a good
idea--putting something in debug only that on construction actually recomputed
the partial hash and checked to see if it was valid.)

[ahendrickson, 2011/11/13 21:15:20]

I'd like to be able to set the partial hash in unit tests.

[Randy Smith (Not in Mondays), 2011/11/15 18:35:25]

Why can't that be done in the constructor?

[ahendrickson, 2011/11/16 15:41:08]

Done.

+
+  // Sets |hash| with sha256 digest for the file.
   // Returns true if digest is successfully calculated.
   virtual bool GetSha256Hash(std::string* hash);