Clean up CodeItemAccessors and Compact/StandardDexFile

Change constructor to use a reference to a dex file.

Remove duplicated logic for GetCodeItemSize.

Bug: 63756964
Test: test-art-host
Change-Id: I69af8b93abdf6bdfa4454e16db8f4e75883bca46
diff --git a/compiler/exception_test.cc b/compiler/exception_test.cc
index 8f7ab05..7bacacf 100644
--- a/compiler/exception_test.cc
+++ b/compiler/exception_test.cc
@@ -130,7 +130,7 @@
 
 TEST_F(ExceptionTest, FindCatchHandler) {
   ScopedObjectAccess soa(Thread::Current());
-  CodeItemDataAccessor accessor(dex_, dex_->GetCodeItem(method_f_->GetCodeItemOffset()));
+  CodeItemDataAccessor accessor(*dex_, dex_->GetCodeItem(method_f_->GetCodeItemOffset()));
 
   ASSERT_TRUE(accessor.HasCodeItem());