IndexedDB: Convert decoding functions to pass StringPieces vs. pointers

content/browser/indexed_db/leveldb/leveldb_slice.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 CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_SLICE_H_
 #define CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_SLICE_H_
 
 #include <vector>
 
 #include "base/logging.h"
+#include "base/strings/string_piece.h"
 
 namespace content {
 
 class LevelDBSlice {
  public:
   LevelDBSlice(const char* begin, const char* end) : begin_(begin), end_(end) {
     DCHECK_GE(end_, begin_);
   }
 
   explicit LevelDBSlice(const std::vector<char>& v)
       : begin_(v.empty() ? NULL : &*v.begin()), end_(begin_ + v.size()) {
     DCHECK_GE(end_, begin_);
   }
 
+  explicit LevelDBSlice(const std::string& v)
+      : begin_(v.data()), end_(v.data() + v.size()) {
+    DCHECK_GE(end_, begin_);
+  }
+
   ~LevelDBSlice() {}
 
   const char* begin() const { return begin_; }
   const char* end() const { return end_; }
 
+  base::StringPiece AsStringPiece() const {
+    return base::StringPiece(begin_, end_ - begin_);
+  }
+
  private:
   const char* begin_;
   const char* end_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_SLICE_H_