[debugger] track debugger feature usage via histogram.

src/profiler/cpu-profiler.cc

Index: src/profiler/cpu-profiler.cc
diff --git a/src/profiler/cpu-profiler.cc b/src/profiler/cpu-profiler.cc
index fa41198e571a831c30239df88c12a42efd9c7ff4..bbddc873b1c0336ab0af91a12e38f3ba93dd64fa 100644
--- a/src/profiler/cpu-profiler.cc
+++ b/src/profiler/cpu-profiler.cc
@@ -4,6 +4,7 @@
 
 #include "src/profiler/cpu-profiler.h"
 
+#include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/frames-inl.h"
 #include "src/locked-queue-inl.h"
@@ -438,6 +439,7 @@ void CpuProfiler::StartProfiling(const char* title, bool record_samples) {
 
 void CpuProfiler::StartProfiling(String* title, bool record_samples) {
   StartProfiling(profiles_->GetName(title), record_samples);
+  isolate_->debug()->feature_tracker()->Track(DebugFeatureTracker::kProfiler);
 }