Move ArtField to ObjPtr

Added EXPECT_OBJ_PTR_EQ and variants to gtests.

Fixed moving GC bugs in:
ClassLinker::CreatePathClassLoader
ClassLinkerTest: StaticFields

ObjPtr Decode call sites: 186 -> 181.

Some tests fail due to ResolvedFieldAccessTest, will fix in follow
up CL.

Bug: 31113334

Test: test-art-host CC baker

Change-Id: I8b266ad00f3c20c8cbe7cfdf280d175083df0b88
diff --git a/runtime/class_linker_test.cc b/runtime/class_linker_test.cc
index 451b752..3c12b18 100644
--- a/runtime/class_linker_test.cc
+++ b/runtime/class_linker_test.cc
@@ -243,10 +243,10 @@
         kRuntimePointerSize));
   }
 
-  void AssertField(mirror::Class* klass, ArtField* field)
+  void AssertField(ObjPtr<mirror::Class> klass, ArtField* field)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     EXPECT_TRUE(field != nullptr);
-    EXPECT_EQ(klass, field->GetDeclaringClass());
+    EXPECT_OBJ_PTR_EQ(klass, field->GetDeclaringClass());
     EXPECT_TRUE(field->GetName() != nullptr);
     EXPECT_TRUE(field->GetType<true>() != nullptr);
   }
@@ -358,7 +358,7 @@
     MemberOffset current_ref_offset = start_ref_offset;
     for (size_t i = 0; i < klass->NumInstanceFields(); i++) {
       ArtField* field = klass->GetInstanceField(i);
-      mirror::Class* field_type = field->GetType<true>();
+      ObjPtr<mirror::Class> field_type = field->GetType<true>();
       ASSERT_TRUE(field_type != nullptr);
       if (!field->IsPrimitiveType()) {
         ASSERT_TRUE(!field_type->IsPrimitive());
@@ -1018,8 +1018,8 @@
                                                         "Ljava/lang/String;");
   EXPECT_EQ(s8->GetTypeAsPrimitiveType(), Primitive::kPrimNot);
   EXPECT_TRUE(s8->GetObject(statics.Get())->AsString()->Equals("android"));
-  s8->SetObject<false>(s8->GetDeclaringClass(),
-                       mirror::String::AllocFromModifiedUtf8(soa.Self(), "robot"));
+  mirror::String* str_value = mirror::String::AllocFromModifiedUtf8(soa.Self(), "robot");
+  s8->SetObject<false>(s8->GetDeclaringClass(), str_value);
 
   // TODO: Remove EXPECT_FALSE when GCC can handle EXPECT_EQ
   // http://code.google.com/p/googletest/issues/detail?id=322