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

src/platform-freebsd.cc

Index: src/platform-freebsd.cc
diff --git a/src/platform-freebsd.cc b/src/platform-freebsd.cc
index 6d1bccda99fc999ccddfaafdf974e93ddde4264e..511759c485e245891dd41a2fa792128e91915f91 100644
--- a/src/platform-freebsd.cc
+++ b/src/platform-freebsd.cc
@@ -678,8 +678,9 @@ 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.
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
@@ -700,7 +701,6 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #endif
   sampler->SampleStack(sample);
   sampler->Tick(sample);
-  CpuProfiler::FinishTickSampleEvent(isolate);
 }
 
 
@@ -884,11 +884,6 @@ Sampler::~Sampler() {
 }
 
 
-void Sampler::DoSample() {
-  // TODO(rogulenko): implement
-}
-
-
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);