Differential updates for components.

extensions/common/crx_file.h

 // Copyright (c) 2012 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_COMMON_CRX_FILE_H_
 #define EXTENSIONS_COMMON_CRX_FILE_H_
 
 #include <sys/types.h>
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 42 matching lines @@
   // additional information.
   // Use this constructor and then .header() to obtain the Header
   // for writing out to a CRX file.
   static scoped_ptr<CrxFile> Create(const uint32 key_size,
                                     const uint32 signature_size,
                                     Error* error);
 
   // Returns the header structure for writing out to a CRX file.
   const Header& header() const { return header_; }
 
+  // Checks a valid |header| to determine whether or not the CRX represents a
+  // differential CRX.
+  static bool HeaderIsDelta(const Header& header);
+
  private:
   Header header_;
 
   // Constructor is private. Clients should use static factory methods above.
   explicit CrxFile(const Header& header);
 
   // Checks the |header| for validity and returns true if the values are valid.
   // If false is returned, more detailed error code is returned in |error|.
   static bool HeaderIsValid(const Header& header, Error* error);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_CRX_FILE_H_