Move most of art::Thread to ObjPtr

Bug: 31113334

Test: test-art-host

Change-Id: I73d0de3c875d3ec3d732034fdc961dae79ef4070
diff --git a/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc b/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
index bf1d4ea..a3e5b55 100644
--- a/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
+++ b/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
@@ -705,7 +705,7 @@
       QuickExceptionHandler::DumpFramesWithType(self, true);
     }
 
-    mirror::Throwable* pending_exception = nullptr;
+    ObjPtr<mirror::Throwable> pending_exception;
     bool from_code = false;
     self->PopDeoptimizationContext(&result, &pending_exception, /* out */ &from_code);