Simplify isolates access during stack iteration (WAS: Move SafeStackFrameIterator::active_count_...)

src/cpu-profiler.cc

Index: src/cpu-profiler.cc
diff --git a/src/cpu-profiler.cc b/src/cpu-profiler.cc
index 082e2532ebce5363cef9d669e7494c8909f11e5b..3894748174a98862121b1d471ec3a94337389d9a 100644
--- a/src/cpu-profiler.cc
+++ b/src/cpu-profiler.cc
@@ -184,12 +184,13 @@ void ProfilerEventsProcessor::RegExpCodeCreateEvent(
 void ProfilerEventsProcessor::AddCurrentStack() {
   TickSampleEventRecord record;
   TickSample* sample = &record.sample;
-  sample->state = Isolate::Current()->current_vm_state();
+  Isolate* isolate = Isolate::Current();
+  sample->state = isolate->current_vm_state();
   sample->pc = reinterpret_cast<Address>(sample);  // Not NULL.
   sample->tos = NULL;
   sample->has_external_callback = false;
   sample->frames_count = 0;
-  for (StackTraceFrameIterator it;
+  for (StackTraceFrameIterator it(isolate);
        !it.done() && sample->frames_count < TickSample::kMaxFramesCount;
        it.Advance()) {
     sample->stack[sample->frames_count++] = it.frame()->pc();