Add trampoline symbols to native debug info.

The debugger needs them to unwind through the trampolines and to
understand what is happening in the call stack.

Change-Id: Ia554058c3796788adcd7336d620a7734eb366905
diff --git a/compiler/debug/elf_debug_info_writer.h b/compiler/debug/elf_debug_info_writer.h
index af74d4c..a6e6f8b 100644
--- a/compiler/debug/elf_debug_info_writer.h
+++ b/compiler/debug/elf_debug_info_writer.h
@@ -46,6 +46,7 @@
 static std::vector<const char*> GetParamNames(const MethodDebugInfo* mi) {
   std::vector<const char*> names;
   if (mi->code_item != nullptr) {
+    DCHECK(mi->dex_file != nullptr);
     const uint8_t* stream = mi->dex_file->GetDebugInfoStream(mi->code_item);
     if (stream != nullptr) {
       DecodeUnsignedLeb128(&stream);  // line.
@@ -133,6 +134,7 @@
 
     const char* last_dex_class_desc = nullptr;
     for (auto mi : compilation_unit.methods) {
+      DCHECK(mi->dex_file != nullptr);
       const DexFile* dex = mi->dex_file;
       const DexFile::CodeItem* dex_code = mi->code_item;
       const DexFile::MethodId& dex_method = dex->GetMethodId(mi->dex_method_index);