Synchronize with r15594.

src/sampler.cc

Index: src/sampler.cc
diff --git a/src/sampler.cc b/src/sampler.cc
index 91f1bb0ddbfd59761ea4d6db3c8661d181f85ff1..624a96f6092d7f1771337665ecb1b494f73ff607 100644
--- a/src/sampler.cc
+++ b/src/sampler.cc
@@ -685,7 +685,8 @@ Sampler::Sampler(Isolate* isolate, int interval)
       interval_(interval),
       profiling_(false),
       active_(false),
-      samples_taken_(0) {
+      is_counting_samples_(false),
+      js_and_external_sample_count_(0) {
   data_ = new PlatformData;
 }
 
@@ -715,7 +716,11 @@ void Sampler::SampleStack(const RegisterState& state) {
   TickSample sample_obj;
   if (sample == NULL) sample = &sample_obj;
   sample->Init(isolate_, state);
-  if (++samples_taken_ < 0) samples_taken_ = 0;
+  if (is_counting_samples_) {
+    if (sample->state == JS || sample->state == EXTERNAL) {
+      ++js_and_external_sample_count_;
+    }
+  }
   Tick(sample);
 }