[Storage] Consoliation of BlobItems with small size

storage/common/data_element.h

 // Copyright 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_COMMON_DATA_ELEMENT_H_
 #define STORAGE_COMMON_DATA_ELEMENT_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 32 matching lines @@
     return expected_modification_time_;
   }
 
   // Sets TYPE_BYTES data. This copies the given data into the element.
   void SetToBytes(const char* bytes, int bytes_len) {
     type_ = TYPE_BYTES;
     buf_.assign(bytes, bytes + bytes_len);
     length_ = buf_.size();
   }
 
+  // Sets TYPE_BYTES data, and clears the internal bytes buffer.
+  // For use with AppendBytes.
+  void SetToEmptyBytes() {
+    type_ = TYPE_BYTES;
+    buf_.clear();
+    length_ = 0;
+    bytes_ = nullptr;
+  }
+
+  // Copies and appends the given data into the element. SetToEmptyBytes or
+  // SetToBytes must be called before this method.
+  void AppendBytes(const char* bytes, int bytes_len) {
+    DCHECK_EQ(type_, TYPE_BYTES);
+    DCHECK_NE(length_, kuint64max);
+    DCHECK(!bytes_);
+    buf_.insert(buf_.end(), bytes, bytes + bytes_len);
+    length_ = buf_.size();
+  }
+
   // Sets TYPE_BYTES data. This does NOT copy the given data and the caller
   // should make sure the data is alive when this element is accessed.
+  // You cannot use AppendBytes with this method.
   void SetToSharedBytes(const char* bytes, int bytes_len) {
     type_ = TYPE_BYTES;
     bytes_ = bytes;
     length_ = bytes_len;
   }
 
   // Sets TYPE_FILE data.
   void SetToFilePath(const base::FilePath& path) {
     SetToFilePathRange(path, 0, kuint64max, base::Time());
   }
@@ skipping 53 matching lines @@
 }
 
 inline bool operator!=(const DataElement& a, const DataElement& b) {
   return !(a == b);
 }
 #endif  // defined(UNIT_TEST)
 
 }  // namespace storage
 
 #endif  // STORAGE_COMMON_DATA_ELEMENT_H_