Clean up some uses of "auto".

Make actual types more explicit, either by replacing "auto"
with actual type or by assigning std::pair<> elements of
an "auto" variable to typed variables. Avoid binding const
references to temporaries. Avoid copying a container.

Test: m test-art-host-gtest
Change-Id: I1a59f9ba1ee15950cacfc5853bd010c1726de603
diff --git a/compiler/optimizing/code_generator.h b/compiler/optimizing/code_generator.h
index ea463ee..9ef692a 100644
--- a/compiler/optimizing/code_generator.h
+++ b/compiler/optimizing/code_generator.h
@@ -842,7 +842,7 @@
     const uint32_t dex_pc = instruction->GetDexPc();
     auto iter = slow_path_map_.find(dex_pc);
     if (iter != slow_path_map_.end()) {
-      auto candidates = iter->second;
+      const ArenaVector<std::pair<InstructionType*, SlowPathCode*>>& candidates = iter->second;
       for (const auto& it : candidates) {
         InstructionType* other_instruction = it.first;
         SlowPathCodeType* other_slow_path = down_cast<SlowPathCodeType*>(it.second);