Move CrxFile, FileReader, ExtensionResource to src/extensions.

extensions/common/constants.h

Index: extensions/common/constants.h
diff --git a/extensions/common/constants.h b/extensions/common/constants.h
index f601b38eb8925d43c494b44a4f31b86dcdc7eea8..31a49851ffcac7b23b8d23c74c6e711f48176fe7 100644
--- a/extensions/common/constants.h
+++ b/extensions/common/constants.h
@@ -5,11 +5,25 @@
 #ifndef EXTENSIONS_COMMON_CONSTANTS_H_
 #define EXTENSIONS_COMMON_CONSTANTS_H_
 
+#include "base/files/file_path.h"
+
 namespace extensions {
 
 // Scheme we serve extension content from.
 extern const char kExtensionScheme[];
 
+  // The name of the manifest inside an extension.
+extern const base::FilePath::CharType kManifestFilename[];
+
+  // The name of locale folder inside an extension.
+extern const base::FilePath::CharType kLocaleFolder[];
+
+  // The name of the messages file inside an extension.
+extern const base::FilePath::CharType kMessagesFilename[];
+
+// The base directory for subdirectories with platform-specific code.
+extern const base::FilePath::CharType kPlatformSpecificFolder[];
+
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_CONSTANTS_H_