Don't default-construct std::strings and then assign them.

Change-Id: I8c994d1e6a8d2ebe52eaa4f0132e0deb2ecfa5f3
diff --git a/src/compiler/codegen/arm/ArchUtility.cc b/src/compiler/codegen/arm/ArchUtility.cc
index b702682..52fb018 100644
--- a/src/compiler/codegen/arm/ArchUtility.cc
+++ b/src/compiler/codegen/arm/ArchUtility.cc
@@ -449,10 +449,9 @@
 
     const art::DexFile::MethodId& method_id =
         cUnit->dex_file->GetMethodId(cUnit->method_idx);
-    std::string signature = cUnit->dex_file->GetMethodSignature(method_id);
-    std::string name = cUnit->dex_file->GetMethodName(method_id);
-    std::string descriptor =
-        cUnit->dex_file->GetMethodDeclaringClassDescriptor(method_id);
+    std::string signature(cUnit->dex_file->GetMethodSignature(method_id));
+    std::string name(cUnit->dex_file->GetMethodName(method_id));
+    std::string descriptor(cUnit->dex_file->GetMethodDeclaringClassDescriptor(method_id));
 
     // Dump mapping table
     if (cUnit->mappingTable.size() > 0) {