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

src/runtime-profiler.cc

Index: src/runtime-profiler.cc
diff --git a/src/runtime-profiler.cc b/src/runtime-profiler.cc
index c6e2b465892b4d6e7c0242ec86bc1c9cdf9a6a44..28755e3ebef77cd11c2beb460adede8460fd5b4d 100644
--- a/src/runtime-profiler.cc
+++ b/src/runtime-profiler.cc
@@ -258,7 +258,7 @@ void RuntimeProfiler::OptimizeNow() {
   JSFunction* samples[kSamplerFrameCount];
   int sample_count = 0;
   int frame_count = 0;
-  for (JavaScriptFrameIterator it;
+  for (JavaScriptFrameIterator it(isolate_);
        frame_count++ < kSamplerFrameCount && !it.done();
        it.Advance()) {
     JavaScriptFrame* frame = it.frame();