Interning image strings

Change-Id: I7e93b3975fe43d91d00b8185b65e8e0fd67ff6f4
diff --git a/src/compiler/Ralloc.cc b/src/compiler/Ralloc.cc
index aaec17b..2161949 100644
--- a/src/compiler/Ralloc.cc
+++ b/src/compiler/Ralloc.cc
@@ -106,7 +106,7 @@
             // Skip past "this"
             sReg++;
         }
-        String* shorty = cUnit->method->GetShorty();
+        const String* shorty = cUnit->method->GetShorty();
         for (int i = 1; i < shorty->GetLength(); i++) {
             char arg = shorty->CharAt(i);
             // Is it wide?