Use stored Isolate pointer instead of Isolate::Current()

src/cpu-profiler.cc

Index: src/cpu-profiler.cc
diff --git a/src/cpu-profiler.cc b/src/cpu-profiler.cc
index be64dd77ac93c041e919799b901aaf2709cb1556..b3800f58771af4383e97e2ceefd15afc67856af7 100644
--- a/src/cpu-profiler.cc
+++ b/src/cpu-profiler.cc
@@ -62,10 +62,9 @@ void ProfilerEventsProcessor::Enqueue(const CodeEventsContainer& event) {
 }
 
 
-void ProfilerEventsProcessor::AddCurrentStack() {
+void ProfilerEventsProcessor::AddCurrentStack(Isolate* isolate) {
   TickSampleEventRecord record(enqueue_order_);
   TickSample* sample = &record.sample;
-  Isolate* isolate = Isolate::Current();
   sample->state = isolate->current_vm_state();
   sample->pc = reinterpret_cast<Address>(sample);  // Not NULL.
   for (StackTraceFrameIterator it(isolate);
@@ -428,7 +427,7 @@ void CpuProfiler::StartProfiling(const char* title, bool record_samples) {
   if (profiles_->StartProfiling(title, next_profile_uid_++, record_samples)) {
     StartProcessorIfNotStarted();
   }
-  processor_->AddCurrentStack();
+  processor_->AddCurrentStack(isolate_);
 }