Invoke CallToRuntime via Thread instead of ObjectPools.

runtime/vm/assembler_arm64.cc

Index: runtime/vm/assembler_arm64.cc
diff --git a/runtime/vm/assembler_arm64.cc b/runtime/vm/assembler_arm64.cc
index 70b2f2ce8b441ceada649b67350e387b917eeee0..a481b7b71b646222f362c76103eaa2006a579c92 100644
--- a/runtime/vm/assembler_arm64.cc
+++ b/runtime/vm/assembler_arm64.cc
@@ -612,6 +612,13 @@ void Assembler::BranchLinkPatchable(const StubEntry& stub_entry) {
 }
 
 
+void Assembler::BranchLinkToRuntime() {
+  ldr(LR, Address(THR, Thread::call_to_runtime_entry_point_offset()));
+  ldr(CODE_REG, Address(THR, Thread::call_to_runtime_stub_offset()));
+  blr(LR);
+}
+
+
 void Assembler::BranchLinkWithEquivalence(const StubEntry& stub_entry,
                                           const Object& equivalence) {
   const Code& target = Code::Handle(stub_entry.code());