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

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index a570868e51fab61671cc3e5c78126b35ec5153d8..a216f6e4cacd2561cb983550ed64d6974dbd095f 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -819,8 +819,9 @@ class SamplerThread : public Thread {
 
   void SampleContext(Sampler* sampler) {
     thread_act_t profiled_thread = sampler->platform_data()->profiled_thread();
-    TickSample* sample = CpuProfiler::StartTickSampleEvent(sampler->isolate());
-    if (sample == NULL) return;
+    TickSample sample_obj;
+    TickSample* sample = CpuProfiler::TickSampleEvent(sampler->isolate());
+    if (sample == NULL) sample = &sample_obj;
 
     if (KERN_SUCCESS != thread_suspend(profiled_thread)) return;
 
@@ -857,7 +858,6 @@ class SamplerThread : public Thread {
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
-    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     thread_resume(profiled_thread);
   }
 
@@ -910,11 +910,6 @@ Sampler::~Sampler() {
 }
 
 
-void Sampler::DoSample() {
-  // TODO(rogulenko): implement
-}
-
-
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);