Fix a few literals and assertions.

Change-Id: I0a1e9db607ec7325e17568b034ba90e68d2298f9
diff --git a/runtime/mirror/dex_cache-inl.h b/runtime/mirror/dex_cache-inl.h
index 1cb437e..bfb9eb5 100644
--- a/runtime/mirror/dex_cache-inl.h
+++ b/runtime/mirror/dex_cache-inl.h
@@ -51,7 +51,7 @@
 
 inline ArtField* DexCache::GetResolvedField(uint32_t idx, size_t ptr_size) {
   ArtField* field = nullptr;
-  if (ptr_size == 8) {
+  if (ptr_size == 8u) {
     field = reinterpret_cast<ArtField*>(
         static_cast<uintptr_t>(GetResolvedFields()->AsLongArray()->GetWithoutChecks(idx)));
   } else {
@@ -66,7 +66,7 @@
 }
 
 inline void DexCache::SetResolvedField(uint32_t idx, ArtField* field, size_t ptr_size) {
-  if (ptr_size == 8) {
+  if (ptr_size == 8u) {
     GetResolvedFields()->AsLongArray()->Set(
         idx, static_cast<uint64_t>(reinterpret_cast<uintptr_t>(field)));
   } else {