Fix compiler warnings.

Added GetReference, GetHandle to StackHandleScope to prevent the
compiler from optimizing away these loads/stores from inline
functions.

Change-Id: I4db02dd3194665d844292e74e3a7d7c80e730e06
diff --git a/runtime/mirror/dex_cache-inl.h b/runtime/mirror/dex_cache-inl.h
index f59c3a2..7e40f64 100644
--- a/runtime/mirror/dex_cache-inl.h
+++ b/runtime/mirror/dex_cache-inl.h
@@ -19,6 +19,8 @@
 
 #include "dex_cache.h"
 
+#include "runtime.h"
+
 namespace art {
 namespace mirror {