Add an API to unpack Zip files directly from and to file descriptors.

chrome/common/zip_internal.h

Index: chrome/common/zip_internal.h
diff --git a/chrome/common/zip_internal.h b/chrome/common/zip_internal.h
index 3f750eac7c3e1c8091d6f7f761155d5f1f02a2ff..db40a4cd29e0daaa13652b1dba0c5da3b31d291b 100644
--- a/chrome/common/zip_internal.h
+++ b/chrome/common/zip_internal.h
@@ -20,6 +20,11 @@ namespace internal {
 // Windows.
 unzFile OpenForUnzipping(const std::string& file_name_utf8);
 
+#if defined(OS_POSIX)
+// Opens the file referred to by |zip_fd| for unzipping.
+unzFile OpenFdForUnzipping(int zip_fd);
+#endif
+
 // Opens the given file name in UTF-8 for zipping, with some setup for
 // Windows. |append_flag| will be passed to zipOpen2().
 zipFile OpenForZipping(const std::string& file_name_utf8, int append_flag);