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

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index b39dfc0eef8aa6132fee8de5ab519d03dcabcb98..089ea38d9a1bb2e0eb11de6d6f1551b0a5268ee3 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -692,8 +692,9 @@ class SamplerThread : public Thread {
     CONTEXT context;
     memset(&context, 0, sizeof(context));
 
-    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;
 
     static const DWORD kSuspendFailed = static_cast<DWORD>(-1);
     if (SuspendThread(profiled_thread) == kSuspendFailed) return;
@@ -713,7 +714,6 @@ class SamplerThread : public Thread {
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
-    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     ResumeThread(profiled_thread);
   }
 
@@ -768,11 +768,6 @@ Sampler::~Sampler() {
 }
 
 
-void Sampler::DoSample() {
-  // TODO(rogulenko): implement
-}
-
-
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);