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 8fbcdd0a9d1f79b0d868a5ec91e2b1db7ffb4330..dacf975b0906a71dea0d02ea556093087b2a1206 100644
--- a/content/browser/download/base_file.h
+++ b/content/browser/download/base_file.h
@@ -32,6 +32,7 @@ class CONTENT_EXPORT BaseFile {
            const GURL& source_url,
            const GURL& referrer_url,
            int64 received_bytes,
+           const std::string& initial_hash,

[Randy Smith (Not in Mondays), 2011/11/16 18:29:27]

In the cases in which we specify an initial_hash, we're going to want to be
specifying an existing file and an offset within that file at which to start,
correct?  Should those be here as well/how are you planning to specify those?

[ahendrickson, 2011/11/19 20:18:03]

Those are already here.

file_stream will be used to specify the location of the file that already has
data, or for restarts the location that we've already decided on.

received_bytes will be non-zero for files that already have data (continued).

[Randy Smith (Not in Mondays), 2011/11/21 02:10:16]

file_stream is fairly often not set; are you making the design decision to set
it always on the continuation pathway?  I'm uncomfortable with that, both
because I don't like that file stream is here (I don't understand the use cases
in which the download system needs to be passed a file descriptor rather than a
file name) and because it represents yet more conditionals as we go through the
code.  
D'oh; right.

[ahendrickson, 2011/11/21 20:34:46]

My mistake; the file is specified in full_path, not file_stream.

BaseFile doesn't know the difference between the intermediate and final files.

When we discover an existing download item, we will set DownloadCreateInfo's
save_info.file_path to the current file name that we are writing to.  When
DownloadFile is constructed, it uses that value to open the file.

            const linked_ptr<net::FileStream>& file_stream);
   virtual ~BaseFile();
 
@@ -64,7 +65,7 @@ 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.
+  // Gets |hash| with sha256 digest for the file.  May be partial.
   // Returns true if digest is successfully calculated.
   virtual bool GetSha256Hash(std::string* hash);