Invoke CallToRuntime via Thread instead of ObjectPools.

runtime/vm/assembler_x64.cc

Index: runtime/vm/assembler_x64.cc
diff --git a/runtime/vm/assembler_x64.cc b/runtime/vm/assembler_x64.cc
index e80efe669037659e09abc24849d82386bb289927..1418548fd00dc96c65bdc8215841e451d4f1317b 100644
--- a/runtime/vm/assembler_x64.cc
+++ b/runtime/vm/assembler_x64.cc
@@ -117,6 +117,13 @@ void Assembler::Call(const StubEntry& stub_entry) {
 }
 
 
+void Assembler::CallToRuntime() {
+  movq(TMP, Address(THR, Thread::call_to_runtime_entry_point_offset()));
+  movq(CODE_REG, Address(THR, Thread::call_to_runtime_stub_offset()));
+  call(TMP);
+}
+
+
 void Assembler::pushq(Register reg) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitRegisterREX(reg, REX_NONE);