Add timestamps to CPU profile samples.

src/cpu-profiler.cc

Index: src/cpu-profiler.cc
diff --git a/src/cpu-profiler.cc b/src/cpu-profiler.cc
index 41f3e986444b9d2371ef4a2a707ae35778084f6e..6128c2c8639b8e290f06dde135a65ee81a040030 100644
--- a/src/cpu-profiler.cc
+++ b/src/cpu-profiler.cc
@@ -432,7 +432,6 @@ void CpuProfiler::StartProfiling(const char* title, bool record_samples) {
   if (profiles_->StartProfiling(title, record_samples)) {
     StartProcessorIfNotStarted();
   }
-  processor_->AddCurrentStack(isolate_);
 }
 
 
@@ -463,6 +462,7 @@ void CpuProfiler::StartProcessorIfNotStarted() {
     // Enable stack sampling.
     sampler->SetHasProcessingThread(true);
     sampler->IncreaseProfilingDepth();
+    processor_->AddCurrentStack(isolate_);
     processor_->StartSynchronously();
   }
 }