ObjPtr<>-ify tests using ClassLinker::FindClass().

ClassLinker::FindClass() returns a non-ObjPtr<> reference
but it has a lot of uses, so we shall change the uses in
a few steps. This change deals with several tests.

Test: Rely on TreeHugger.
Bug: 31113334
Change-Id: Ib75e20e7ebaff01fb607a09f96675f8cf397ae52
diff --git a/compiler/common_compiler_test.cc b/compiler/common_compiler_test.cc
index 96a0c1b..a7f16d3 100644
--- a/compiler/common_compiler_test.cc
+++ b/compiler/common_compiler_test.cc
@@ -123,7 +123,7 @@
   Thread* self = Thread::Current();
   StackHandleScope<1> hs(self);
   Handle<mirror::ClassLoader> loader(hs.NewHandle(class_loader));
-  mirror::Class* klass = class_linker_->FindClass(self, class_descriptor.c_str(), loader);
+  ObjPtr<mirror::Class> klass = class_linker_->FindClass(self, class_descriptor.c_str(), loader);
   CHECK(klass != nullptr) << "Class not found " << class_name;
   PointerSize pointer_size = class_linker_->GetImagePointerSize();
   for (auto& m : klass->GetMethods(pointer_size)) {
@@ -222,7 +222,7 @@
   Thread* self = Thread::Current();
   StackHandleScope<1> hs(self);
   Handle<mirror::ClassLoader> loader(hs.NewHandle(class_loader));
-  mirror::Class* klass = class_linker_->FindClass(self, class_descriptor.c_str(), loader);
+  ObjPtr<mirror::Class> klass = class_linker_->FindClass(self, class_descriptor.c_str(), loader);
   CHECK(klass != nullptr) << "Class not found " << class_name;
   auto pointer_size = class_linker_->GetImagePointerSize();
   for (auto& m : klass->GetMethods(pointer_size)) {
@@ -244,7 +244,8 @@
                                              const char* signature) {
   std::string class_descriptor(DotToDescriptor(class_name));
   Thread* self = Thread::Current();
-  mirror::Class* klass = class_linker_->FindClass(self, class_descriptor.c_str(), class_loader);
+  ObjPtr<mirror::Class> klass =
+      class_linker_->FindClass(self, class_descriptor.c_str(), class_loader);
   CHECK(klass != nullptr) << "Class not found " << class_name;
   auto pointer_size = class_linker_->GetImagePointerSize();
   ArtMethod* method = klass->FindClassMethod(method_name, signature, pointer_size);
@@ -258,7 +259,8 @@
                                               const char* signature) {
   std::string class_descriptor(DotToDescriptor(class_name));
   Thread* self = Thread::Current();
-  mirror::Class* klass = class_linker_->FindClass(self, class_descriptor.c_str(), class_loader);
+  ObjPtr<mirror::Class> klass =
+      class_linker_->FindClass(self, class_descriptor.c_str(), class_loader);
   CHECK(klass != nullptr) << "Class not found " << class_name;
   auto pointer_size = class_linker_->GetImagePointerSize();
   ArtMethod* method = klass->FindClassMethod(method_name, signature, pointer_size);