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

storage/browser/blob/blob_storage_registry.h

 // Copyright 2015 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_STORAGE_REGISTRY_H_
 #define STORAGE_BROWSER_BLOB_BLOB_STORAGE_REGISTRY_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 14 matching lines @@
 
 // This class stores the blob data in the various states of construction, as
 // well as URL mappings to blob uuids.
 // Implementation notes:
 // * There is no implicit refcounting in this class, except for setting the
 //   refcount to 1 on registration.
 // * When removing a uuid registration, we do not check for URL mappings to that
 //   uuid. The user must keep track of these.
 class STORAGE_EXPORT BlobStorageRegistry {
  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)>;
+
   enum class BlobState {
     // The blob is pending transportation from the renderer. This is the default
     // state on entry construction.
     PENDING,
     // The blob is complete and can be read from.
     COMPLETE,
     // The blob is broken and no longer holds data. This happens when there was
     // a problem constructing the blob, or we've run out of memory.
     BROKEN
   };
 
   struct STORAGE_EXPORT Entry {
     size_t refcount;
     BlobState state;
-    std::vector<base::Callback<void(bool)>> build_completion_callbacks;
+    std::vector<BlobConstructedCallback> build_completion_callbacks;
 
     // Only applicable if the state == BROKEN.
     IPCBlobCreationCancelCode broken_reason =
         IPCBlobCreationCancelCode::UNKNOWN;
 
     // data and data_builder are mutually exclusive.
     std::unique_ptr<InternalBlobData> data;
     std::unique_ptr<InternalBlobData::Builder> data_builder;
 
     std::string content_type;
@@ skipping 53 matching lines @@
   using URLMap = std::map<GURL, std::string>;
 
   BlobMap blob_map_;
   URLMap url_to_uuid_;
 
   DISALLOW_COPY_AND_ASSIGN(BlobStorageRegistry);
 };
 
 }  // namespace storage
 #endif  // STORAGE_BROWSER_BLOB_BLOB_STORAGE_REGISTRY_H_