[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_data_handle.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_
 #define STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 59 matching lines @@
   std::unique_ptr<BlobReader> CreateReader(
       FileSystemContext* file_system_context,
       base::SequencedTaskRunner* file_task_runner) const;
 
   // May be accessed on any thread.
   const std::string& uuid() const;
   // May be accessed on any thread.
   const std::string& content_type() const;
   // May be accessed on any thread.
   const std::string& content_disposition() const;
+  // May be accessed on any thread. In rare cases where the blob is created
+  // as a file from the renderer, this will be uint64_max.
+  uint64_t size() const;
 
   // This call and the destruction of the returned snapshot must be called
   // on the IO thread. If the blob is broken, then we return a nullptr here.
   // Please do not call this, and use CreateReader instead. It appropriately
   // waits until the blob is built before having a size (see CalculateSize).
   // TODO(dmurph): Make this protected, where only the BlobReader can call it.
   std::unique_ptr<BlobDataSnapshot> CreateSnapshot() const;
 
  private:
   // Internal class whose destructor is guarenteed to be called on the IO
   // thread.
   class BlobDataHandleShared
       : public base::RefCountedThreadSafe<BlobDataHandleShared> {
    public:
     BlobDataHandleShared(const std::string& uuid,
                          const std::string& content_type,
                          const std::string& content_disposition,
+                         uint64_t size,
                          BlobStorageContext* context);
 
    private:
     friend class base::DeleteHelper<BlobDataHandleShared>;
     friend class base::RefCountedThreadSafe<BlobDataHandleShared>;
     friend class BlobDataHandle;
 
     virtual ~BlobDataHandleShared();
 
     const std::string uuid_;
     const std::string content_type_;
     const std::string content_disposition_;
+    const uint64_t size_;
     base::WeakPtr<BlobStorageContext> context_;
 
     DISALLOW_COPY_AND_ASSIGN(BlobDataHandleShared);
   };
 
   friend class BlobStorageContext;
   BlobDataHandle(const std::string& uuid,
                  const std::string& content_type,
                  const std::string& content_disposition,
+                 uint64_t size,
                  BlobStorageContext* context,
                  base::SequencedTaskRunner* io_task_runner);
 
   scoped_refptr<base::SequencedTaskRunner> io_task_runner_;
   scoped_refptr<BlobDataHandleShared> shared_;
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_