[Blob] Fix for resetting reader.

storage/browser/blob/blob_reader.h

Index: storage/browser/blob/blob_reader.h
diff --git a/storage/browser/blob/blob_reader.h b/storage/browser/blob/blob_reader.h
index 54b262f3ef3e910dfcf932c37a87d8b9e85ab8b7..6a68af8ef7c1ca5dbb91d79a16777e5d44d03af6 100644
--- a/storage/browser/blob/blob_reader.h
+++ b/storage/browser/blob/blob_reader.h
@@ -13,6 +13,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "net/base/completion_callback.h"
+#include "net/base/net_errors.h"
 #include "storage/browser/storage_browser_export.h"
 
 class GURL;
@@ -41,6 +42,7 @@ class FileSystemContext;
 //  * There can only be one read happening at a time per reader.
 //  * If a status of Status::NET_ERROR is returned, that means there was an
 //    error and the net_error() variable contains the error code.
+//  * To reuse a reader on the same blob, call the Reset() function.
 // Use a BlobDataHandle to create an instance.
 class STORAGE_EXPORT BlobReader {
  public:
@@ -65,7 +67,8 @@ class STORAGE_EXPORT BlobReader {
 
   // This calculates the total size of the blob, and initializes the reading
   // cursor.
-  //  * This should only be called once per reader.
+  //  * This should only be called once per reader, unless 'Reset' has been
+  //    called.
   //  * Status::Done means that the total_size() value is populated and you can
   //    continue to SetReadRange or Read.
   //  * The 'done' callback is only called if Status::IO_PENDING is returned.
@@ -95,6 +98,10 @@ class STORAGE_EXPORT BlobReader {
   // after this call.
   void Kill();
 
+  // This resets the reader so we can use it again. Usually used in conjunction
+  // with reader_used(). This will invalidate all callbacks.
+  void Reset();
+
   // Returns if all of the blob's items are in memory.
   bool IsInMemory() const;
 
@@ -109,6 +116,9 @@ class STORAGE_EXPORT BlobReader {
   // is called.
   uint64_t total_size() const { return total_size_; }
 
+  // Returns if this reader has been used yet.
+  bool reader_used() const { return reader_used_; }
+
  protected:
   friend class BlobDataHandle;
   friend class BlobReaderTest;
@@ -163,17 +173,17 @@ class STORAGE_EXPORT BlobReader {
   scoped_ptr<FileStreamReaderProvider> file_stream_provider_;
   scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
 
-  int net_error_;
-  bool item_list_populated_ = false;
+  int net_error_ = net::OK;
   std::vector<uint64_t> item_length_list_;
 
   scoped_refptr<net::DrainableIOBuffer> read_buf_;
 
+  bool reader_used_ = false;
   bool total_size_calculated_ = false;
   uint64_t total_size_ = 0;
   uint64_t remaining_bytes_ = 0;
   size_t pending_get_file_info_count_ = 0;
-  std::map<size_t, FileStreamReader*> index_to_reader_;
+  std::map<size_t, scoped_ptr<FileStreamReader>> index_to_reader_;
   size_t current_item_index_ = 0;
   uint64_t current_item_offset_ = 0;