[debugger] track debugger feature usage via histogram.

src/profiler/heap-profiler.cc

 // Copyright 2009-2010 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/profiler/heap-profiler.h"
 
 #include "src/api.h"
+#include "src/debug/debug.h"
 #include "src/profiler/allocation-tracker.h"
 #include "src/profiler/heap-snapshot-generator-inl.h"
 
 namespace v8 {
 namespace internal {
 
 HeapProfiler::HeapProfiler(Heap* heap)
     : ids_(new HeapObjectsMap(heap)),
       names_(new StringsStorage(heap)),
       is_tracking_object_moves_(false) {
@@ skipping 50 matching lines @@
     HeapSnapshotGenerator generator(result, control, resolver, heap());
     if (!generator.GenerateSnapshot()) {
       delete result;
       result = NULL;
     } else {
       snapshots_.Add(result);
     }
   }
   ids_->RemoveDeadEntries();
   is_tracking_object_moves_ = true;
+
+  heap()->isolate()->debug()->feature_tracker()->Track(
+      DebugFeatureTracker::kHeapSnapshot);
+
   return result;
 }
 
 
 void HeapProfiler::StartHeapObjectsTracking(bool track_allocations) {
   ids_->UpdateHeapObjectsMap();
   is_tracking_object_moves_ = true;
   DCHECK(!is_tracking_allocations());
   if (track_allocations) {
     allocation_tracker_.Reset(new AllocationTracker(ids_.get(), names_.get()));
     heap()->DisableInlineAllocation();
+    heap()->isolate()->debug()->feature_tracker()->Track(
+        DebugFeatureTracker::kAllocationTracking);
   }
 }
 
 
 SnapshotObjectId HeapProfiler::PushHeapObjectsStats(OutputStream* stream,
                                                     int64_t* timestamp_us) {
   return ids_->PushHeapObjectsStats(stream, timestamp_us);
 }
 
 
@@ skipping 85 matching lines @@
   ids_.Reset(new HeapObjectsMap(heap()));
   if (!is_tracking_allocations()) is_tracking_object_moves_ = false;
 }
 
 
 Heap* HeapProfiler::heap() const { return ids_->heap(); }
 
 
 }  // namespace internal
 }  // namespace v8