Pass the verify flag to DexFileLoader utilities.

Refactoring-only change.

Also remove unused DexFilerLoader::OpenMemory.

bug: 30972906
bug: 63920015

Test: build.

Change-Id: I7cd4b5787565ab1a3457ce2be6bb14657229c550
diff --git a/runtime/common_runtime_test.cc b/runtime/common_runtime_test.cc
index 0c2e490..d35402f 100644
--- a/runtime/common_runtime_test.cc
+++ b/runtime/common_runtime_test.cc
@@ -373,7 +373,8 @@
   std::string error_msg;
   MemMap::Init();
   static constexpr bool kVerifyChecksum = true;
-  if (!DexFileLoader::Open(location, location, kVerifyChecksum, &error_msg, &dex_files)) {
+  if (!DexFileLoader::Open(
+        location, location, /* verify */ true, kVerifyChecksum, &error_msg, &dex_files)) {
     LOG(FATAL) << "Could not open .dex file '" << location << "': " << error_msg << "\n";
     UNREACHABLE();
   } else {
@@ -572,8 +573,11 @@
   static constexpr bool kVerifyChecksum = true;
   std::string error_msg;
   std::vector<std::unique_ptr<const DexFile>> dex_files;
-  bool success = DexFileLoader::Open(
-      filename.c_str(), filename.c_str(), kVerifyChecksum, &error_msg, &dex_files);
+  bool success = DexFileLoader::Open(filename.c_str(),
+                                     filename.c_str(),
+                                     /* verify */ true,
+                                     kVerifyChecksum,
+                                     &error_msg, &dex_files);
   CHECK(success) << "Failed to open '" << filename << "': " << error_msg;
   for (auto& dex_file : dex_files) {
     CHECK_EQ(PROT_READ, dex_file->GetPermissions());