Improve compiler stats

- report the max size of arena alloc
- report how many virtual or interface invokes were inlined

Change-Id: I82f154a8e25b5e3890181a1aa11346cdc3f93e37
diff --git a/compiler/driver/compiler_driver.h b/compiler/driver/compiler_driver.h
index 42a5bc1..4ef26dd 100644
--- a/compiler/driver/compiler_driver.h
+++ b/compiler/driver/compiler_driver.h
@@ -694,6 +694,7 @@
   // Info for profile guided compilation.
   const ProfileCompilationInfo* const profile_compilation_info_;
 
+  size_t max_arena_alloc_;
   friend class CompileClassVisitor;
   DISALLOW_COPY_AND_ASSIGN(CompilerDriver);
 };