Fix unoptimized code calling a disabled code when --verify-on-transition is enabled.

runtime/vm/stub_code_mips.cc

Index: runtime/vm/stub_code_mips.cc
diff --git a/runtime/vm/stub_code_mips.cc b/runtime/vm/stub_code_mips.cc
index 94e163cda6d8884b8b15560a204cfa3877473719..6df06424f3adf64ae7ca2cf979232b3fc1960b11 100644
--- a/runtime/vm/stub_code_mips.cc
+++ b/runtime/vm/stub_code_mips.cc
@@ -2023,12 +2023,13 @@ void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
   __ sw(T0, Address(SP, 0 * kWordSize));
   __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry, 1);
   __ Comment("OptimizeFunctionStub return");
-  __ lw(CODE_REG, Address(SP, 1 * kWordSize));  // Get Code object
+  __ lw(T0, Address(SP, 1 * kWordSize));  // Get Function object
   __ lw(S4, Address(SP, 2 * kWordSize));  // Restore argument descriptor.
   __ addiu(SP, SP, Immediate(3 * kWordSize));  // Discard argument.
 
-  __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
-  __ LeaveStubFrameAndReturn(T0);
+  __ lw(CODE_REG, FieldAddress(T0, Function::code_offset()));
+  __ lw(T1, FieldAddress(T0, Function::entry_point_offset()));
+  __ LeaveStubFrameAndReturn(T1);
   __ break_(0);
 }