[BlobAsync] Adding better error reporting and some new tests.

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>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/supports_user_data.h"
 #include "storage/browser/storage_browser_export.h"
+#include "storage/common/blob_storage/blob_storage_constants.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
 
 namespace storage {
 
 class BlobDataSnapshot;
 class BlobReader;
 class BlobStorageContext;
 class FileSystemContext;
 
 // BlobDataHandle ensures that the underlying blob (keyed by the uuid) remains
 // in the BlobStorageContext's collection while this object is alive. Anything
 // that needs to keep a blob alive needs to store this handle.
 // When the blob data itself is needed, clients must call the CreateSnapshot()
 // method on the IO thread to create a snapshot of the blob data.  This snapshot
 // is not intended to be persisted, and serves to ensure that the backing
 // resources remain around for the duration of reading the blob.  This snapshot
 // can be read on any thread, but it must be destructed on the IO thread.
 // This object has delete semantics and may be deleted on any thread.
 class STORAGE_EXPORT BlobDataHandle
     : public base::SupportsUserData::Data {
  public:
+  // True means the blob was constructed successfully, and false means that
+  // there was an error, which is reported in the second argument.
+  using BlobConstructedCallback =
+      base::Callback<void(bool, IPCBlobCreationCancelCode)>;
+
   BlobDataHandle(const BlobDataHandle& other);  // May be copied on any thread.
   ~BlobDataHandle() override;                   // May be deleted on any thread.
 
   // Returns if this blob is still constructing. If so, one can use the
   // RunOnConstructionComplete to wait.
   // Must be called on IO thread.
   bool IsBeingBuilt() const;
 
   // Returns if this blob is broken, and there is no data associated with it.
   // Must be called on IO thread.
   bool IsBroken() const;
 
   // The callback will be run on the IO thread when construction of the blob
   // is complete. If construction is already complete, then the task is run
   // immediately on the current message loop (i.e. IO thread).
   // Must be called on IO thread.  Returns if construction successful.
   // Calling this multiple times results in registering multiple
   // completion callbacks.
-  void RunOnConstructionComplete(const base::Callback<void(bool)>& done);
+  void RunOnConstructionComplete(const BlobConstructedCallback& done);
 
   // A BlobReader is used to read the data from the blob.  This object is
   // intended to be transient and should not be stored for any extended period
   // of time.
   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;
@@ skipping 13 matching lines @@
   // 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,
                          BlobStorageContext* context);
 
-    void RunOnConstructionComplete(const base::Callback<void(bool)>& done);
-
-    std::unique_ptr<BlobDataSnapshot> CreateSnapshot() const;
-
    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_;
     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,
                  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_