Revert recent CPU profiler changes because they broke --prof.

src/platform-openbsd.cc

Index: src/platform-openbsd.cc
diff --git a/src/platform-openbsd.cc b/src/platform-openbsd.cc
index f96d9e3031a503c6f81282cc7b8d6bc09232d5c7..408d4dc0f8487e08a8a4277ad8139f4910b6d4de 100644
--- a/src/platform-openbsd.cc
+++ b/src/platform-openbsd.cc
@@ -731,8 +731,9 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
-  TickSample* sample = CpuProfiler::StartTickSampleEvent(isolate);
-  if (sample == NULL) return;
+  TickSample sample_obj;
+  TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
+  if (sample == NULL) sample = &sample_obj;
 
   // Extracting the sample from the context is extremely machine dependent.
   sample->state = isolate->current_vm_state();
@@ -761,7 +762,6 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #endif  // __NetBSD__
   sampler->SampleStack(sample);
   sampler->Tick(sample);
-  CpuProfiler::FinishTickSampleEvent(isolate);
 }
 
 
@@ -964,11 +964,6 @@ Sampler::~Sampler() {
 }
 
 
-void Sampler::DoSample() {
-  // TODO(rogulenko): implement
-}
-
-
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);