Fix for 0-length file problem in content verification

extensions/browser/computed_hashes.h

 // Copyright 2014 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 EXTENSIONS_BROWSER_COMPUTED_HASHES_H_
 #define EXTENSIONS_BROWSER_COMPUTED_HASHES_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
-#include "base/values.h"
+#include "base/memory/scoped_ptr.h"
 
 namespace base {
 class FilePath;
+class ListValue;
 }
 
 namespace extensions {
 
 // A pair of classes for serialization of a set of SHA256 block hashes computed
 // over the files inside an extension.
 class ComputedHashes {
  public:
   class Reader {
    public:
@@ skipping 21 matching lines @@
 
     // Adds hashes for |relative_path|. Should not be called more than once
     // for a given |relative_path|.
     void AddHashes(const base::FilePath& relative_path,
                    int block_size,
                    const std::vector<std::string>& hashes);
 
     bool WriteToFile(const base::FilePath& path);
 
    private:
-    // The top-level object that will be serialized as JSON.
-    base::ListValue file_list_;
+    // Each element of this list contains the path and block hashes for one
+    // file.
+    scoped_ptr<base::ListValue> file_list_;
   };
+
+  // Computes the SHA256 hash of each |block_size| chunk in |contents|, placing
+  // the results into |hashes|.
+  static void ComputeHashesForContent(const std::string& contents,
+                                      size_t block_size,
+                                      std::vector<std::string>* hashes);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_COMPUTED_HASHES_H_