Pass some arguments by const reference.

Test: Rely on TreeHugger.
Bug: 32619234
Change-Id: Ia26277893641dcb3562eaeacaec4e089a978d56a
diff --git a/runtime/oat_file_manager.cc b/runtime/oat_file_manager.cc
index fde0a2c..8efb465 100644
--- a/runtime/oat_file_manager.cc
+++ b/runtime/oat_file_manager.cc
@@ -377,7 +377,7 @@
   }
 }
 
-static bool AreSharedLibrariesOk(const std::string shared_libraries,
+static bool AreSharedLibrariesOk(const std::string& shared_libraries,
                                  std::priority_queue<DexFileAndClassPair>& queue) {
   if (shared_libraries.empty()) {
     if (queue.empty()) {