Refactor Isolate -> Thread in NativeArguments and exception handler jump.

runtime/vm/simulator_mips.cc

Index: runtime/vm/simulator_mips.cc
diff --git a/runtime/vm/simulator_mips.cc b/runtime/vm/simulator_mips.cc
index cd351a7d6ea2c85120d35b43d734d842229ee810..684d81daec9b84174bdf707ef793b115ef4835a4 100644
--- a/runtime/vm/simulator_mips.cc
+++ b/runtime/vm/simulator_mips.cc
@@ -1237,7 +1237,7 @@ void Simulator::DoBreak(Instr *instr) {
       if (redirection->call_kind() == kRuntimeCall) {
         NativeArguments arguments;
         ASSERT(sizeof(NativeArguments) == 4*kWordSize);
-        arguments.isolate_ = reinterpret_cast<Isolate*>(get_register(A0));
+        arguments.thread_ = reinterpret_cast<Thread*>(get_register(A0));
         arguments.argc_tag_ = get_register(A1);
         arguments.argv_ = reinterpret_cast<RawObject*(*)[]>(get_register(A2));
         arguments.retval_ = reinterpret_cast<RawObject**>(get_register(A3));
@@ -2454,7 +2454,7 @@ void Simulator::Longjmp(uword pc,
                         uword fp,
                         RawObject* raw_exception,
                         RawObject* raw_stacktrace,
-                        Isolate* isolate) {
+                        Thread* thread) {
   // Walk over all setjmp buffers (simulated --> C++ transitions)
   // and try to find the setjmp associated with the simulated stack pointer.
   SimulatorSetjmpBuffer* buf = last_setjmp_buffer();
@@ -2466,12 +2466,14 @@ void Simulator::Longjmp(uword pc,
   // The C++ caller has not cleaned up the stack memory of C++ frames.
   // Prepare for unwinding frames by destroying all the stack resources
   // in the previous C++ frames.
+  Isolate* isolate = thread->isolate();
   StackResource::Unwind(isolate);
 
   // Unwind the C++ stack and continue simulation in the target frame.
   set_pc(static_cast<int32_t>(pc));
   set_register(SP, static_cast<int32_t>(sp));
   set_register(FP, static_cast<int32_t>(fp));
+  set_register(THR, reinterpret_cast<int32_t>(thread));
   // Set the tag.
   isolate->set_vm_tag(VMTag::kDartTagId);
   // Clear top exit frame.