Componentize component_updater: Split crx_file code off into its own component.

components/crx_file/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_
+#ifndef COMPONENTS_CRX_FILE_CRX_FILE_H_
+#define COMPONENTS_CRX_FILE_CRX_FILE_H_
 
 #include <sys/types.h>
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 
-namespace extensions {
+namespace crx_file {
 
 // CRX files have a header that includes a magic key, version number, and
 // some signature sizing information. Use CrxFile object to validate whether
 // the header is valid or not.
 class CrxFile {
  public:
   // The size of the magic character sequence at the beginning of each crx
   // file, in bytes. This should be a multiple of 4.
   static const size_t kCrxFileHeaderMagicSize = 4;
 
@@ skipping 44 matching lines @@
   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
+}  // namespace crx_file
 
-#endif  // EXTENSIONS_COMMON_CRX_FILE_H_
+#endif  // COMPONENTS_CRX_FILE_CRX_FILE_H_