Delete ClassHelper and fix compaction bug in GetDirectInterface

Cleanup helps to prevent compaction bugs. Fixed a fairly serious
compaction error caused by calling ClassHelper::GetDirectInterface
without handling the case where it causes thread suspension due to
ResolveType.

Bug: 8981901

Change-Id: I82b3bb6dd48d21eb6ece7aae0733c4a23c2bc408
diff --git a/runtime/interpreter/interpreter_switch_impl.cc b/runtime/interpreter/interpreter_switch_impl.cc
index 859cfc4..c1d24f5 100644
--- a/runtime/interpreter/interpreter_switch_impl.cc
+++ b/runtime/interpreter/interpreter_switch_impl.cc
@@ -258,8 +258,8 @@
             self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                      "Ljava/lang/VirtualMachineError;",
                                      "Returning '%s' that is not instance of return type '%s'",
-                                     ClassHelper(obj_result->GetClass()).GetDescriptor(),
-                                     ClassHelper(return_type).GetDescriptor());
+                                     obj_result->GetClass()->GetDescriptor().c_str(),
+                                     return_type->GetDescriptor().c_str());
             HANDLE_PENDING_EXCEPTION();
           }
         }
@@ -528,7 +528,7 @@
           self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                    "Ljava/lang/VirtualMachineError;",
                                    "Throwing '%s' that is not instance of Throwable",
-                                   ClassHelper(exception->GetClass()).GetDescriptor());
+                                   exception->GetClass()->GetDescriptor().c_str());
         } else {
           self->SetException(shadow_frame.GetCurrentLocationForThrow(), exception->AsThrowable());
         }