Remove unused GetDexRegisterMap arguments.

They are no longer needed in the new encoding.

I reuse the local variables in most places to DCHECK the size
of the decoded register map.  This has one catch though:
We sometimes omit all dex registers, so the DCHECK should be
done only after checking if the map is empty (if applicable).

Test: test-art-host-gtest-stack_map_test
Change-Id: I94b67029842374bc8eb7c9e5eac76fc93a651f24
diff --git a/runtime/stack.cc b/runtime/stack.cc
index 0b3441a..56e47b9 100644
--- a/runtime/stack.cc
+++ b/runtime/stack.cc
@@ -236,14 +236,12 @@
   size_t depth_in_stack_map = current_inlining_depth_ - 1;
 
   DexRegisterMap dex_register_map = IsInInlinedFrame()
-      ? code_info.GetDexRegisterMapAtDepth(depth_in_stack_map,
-                                           stack_map,
-                                           number_of_dex_registers)
-      : code_info.GetDexRegisterMapOf(stack_map, number_of_dex_registers);
-
-  if (!dex_register_map.IsValid()) {
+      ? code_info.GetDexRegisterMapAtDepth(depth_in_stack_map, stack_map)
+      : code_info.GetDexRegisterMapOf(stack_map);
+  if (dex_register_map.empty()) {
     return false;
   }
+  DCHECK_EQ(dex_register_map.size(), number_of_dex_registers);
   DexRegisterLocation::Kind location_kind = dex_register_map.GetLocationKind(vreg);
   switch (location_kind) {
     case DexRegisterLocation::Kind::kInStack: {