Add --image-classes to dex2oat

Change-Id: Ia88f9d302e0f9cd72be2199ee46d212d99864c67
diff --git a/src/dex_file.cc b/src/dex_file.cc
index 208479e..d7517c4 100644
--- a/src/dex_file.cc
+++ b/src/dex_file.cc
@@ -45,7 +45,7 @@
                         reinterpret_cast<const DexFile::ClassDef*>(NULL));
 }
 
-void DexFile::OpenDexFiles(std::vector<const char*>& dex_filenames,
+void DexFile::OpenDexFiles(const std::vector<const char*>& dex_filenames,
                            std::vector<const DexFile*>& dex_files,
                            const std::string& strip_location_prefix) {
   for (size_t i = 0; i < dex_filenames.size(); i++) {