Remove some uses of STL map.

runtime/vm/assembler.cc

Index: runtime/vm/assembler.cc
diff --git a/runtime/vm/assembler.cc b/runtime/vm/assembler.cc
index fe775bf7775b70205ad546f03d19843554a6eaaa..8bb29cab1e46aaa983afd3ca62ff88993cf1d995 100644
--- a/runtime/vm/assembler.cc
+++ b/runtime/vm/assembler.cc
@@ -275,7 +275,7 @@ intptr_t ObjectPoolWrapper::FindObject(ObjectPoolWrapperEntry entry,
   // If the object is not patchable, check if we've already got it in the
   // object pool.
   if (patchable == kNotPatchable) {
-    intptr_t idx = object_pool_index_table_.Lookup(entry);
+    intptr_t idx = object_pool_index_table_.LookupValue(entry);
     if (idx != ObjIndexPair::kNoIndex) {
       return idx;
     }