Added member data to classes to support download resumption.

content/browser/download/download_resource_handler.h

Index: content/browser/download/download_resource_handler.h
diff --git a/content/browser/download/download_resource_handler.h b/content/browser/download/download_resource_handler.h
index 016756c58ad68c336a0055f310e8f0db903b5f23..935a0efa02c8b0608906fb85b619b81216848347 100644
--- a/content/browser/download/download_resource_handler.h
+++ b/content/browser/download/download_resource_handler.h
@@ -11,10 +11,11 @@
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/timer.h"
-#include "content/browser/download/download_file.h"
 #include "content/browser/download/download_id.h"
+#include "content/browser/download/download_types.h"
 #include "content/browser/renderer_host/global_request_id.h"
 #include "content/browser/renderer_host/resource_handler.h"
+#include "net/base/net_errors.h"
 
 class DownloadFileManager;
 class ResourceDispatcherHost;
@@ -79,6 +80,9 @@ class DownloadResourceHandler : public ResourceHandler {
 
   void set_content_disposition(const std::string& content_disposition);
 
+  // Location within the resource at which to start the download.
+  void set_start_offset(int64 bytes) { start_offset_ = bytes; }

[Randy Smith (Not in Mondays), 2011/11/16 21:40:25]

It occurs to me to ask: Should this be in the constructor?  I can imagine
reasons why it wouldn't be, but if it can be, it should be.

[Randy Smith (Not in Mondays), 2011/11/16 21:40:25]

Note that there's an awesome unit-test opportunity here (that we should take) of
trying to download the second half of a local resource and making sure we get
what we expect.  This probably only works if the mock request job supports range
requests.  

[ahendrickson, 2011/11/19 20:18:04]

We have a download ID at construction time (in BufferedResourceHandler), but we
don't have access to the DownloadItem, which has the number of received bytes.

[ahendrickson, 2011/11/19 20:18:04]

Done.  The unit test fails currently, but will succeed (I hope!) once
serialization works for SecureHash.

[Randy Smith (Not in Mondays), 2011/11/21 02:10:17]

We never have access to the DownloadItem on the IO thread.  What's the pathway
by which this setter will get called?  

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

The unit test now succeeds.

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

Changed it to be in the constructor, so this setter is removed.  We will pass in
a DownloadResumeInfo to RDH::BeginDownload(), which will provide the start
offset.

+
   void CheckWriteProgress();
 
   std::string DebugString() const;
@@ -107,6 +111,7 @@ class DownloadResourceHandler : public ResourceHandler {
   base::TimeTicks download_start_time_;  // used to collect stats.
   base::TimeTicks last_read_time_;        // used to collect stats.
   size_t last_buffer_size_;               // used to collect stats.
+  int64 start_offset_;
   static const int kReadBufSize = 32768;  // bytes
   static const int kThrottleTimeMs = 200;  // milliseconds