[debugger] track debugger feature usage via histogram.

R=jochen@chromium.org

Review URL: https://codereview.chromium.org/1478613004

Cr-Commit-Position: refs/heads/master@{#32328}

src/counters.h

@@ -484,7 +484,8 @@ double AggregatedMemoryHistogram<Histogram>::Aggregate(double current_ms,
   HR(gc_idle_time_limit_undershot, V8.GCIdleTimeLimit.Undershot, 0, 10000,    \
      101)                                                                     \
   HR(code_cache_reject_reason, V8.CodeCacheRejectReason, 1, 6, 6)             \
-  HR(errors_thrown_per_context, V8.ErrorsThrownPerContext, 0, 200, 20)
+  HR(errors_thrown_per_context, V8.ErrorsThrownPerContext, 0, 200, 20)        \
+  HR(debug_feature_usage, V8.DebugFeatureUsage, 1, 7, 7)
 
 #define HISTOGRAM_TIMER_LIST(HT)                                              \
   /* Garbage collection timers. */                                            \

src/debug/debug.cc

@@ -43,6 +43,7 @@ Debug::Debug(Isolate* isolate)
       break_on_exception_(false),
       break_on_uncaught_exception_(false),
       debug_info_list_(NULL),
+      feature_tracker_(isolate),
       isolate_(isolate) {
   ThreadInit();
 }
@@ -316,6 +317,15 @@ Handle<Object> BreakLocation::BreakPointObjects() const {
 }
 
 
+void DebugFeatureTracker::Track(DebugFeatureTracker::Feature feature) {
+  uint32_t mask = 1 << feature;
+  // Only count one sample per feature and isolate.
+  if (bitfield_ & mask) return;
+  isolate_->counters()->debug_feature_usage()->AddSample(feature);
+  bitfield_ |= mask;
+}
+
+
 // Threading support.
 void Debug::ThreadInit() {
   thread_local_.break_count_ = 0;
@@ -396,6 +406,9 @@ bool Debug::Load() {
 
   debug_context_ = Handle<Context>::cast(
       isolate_->global_handles()->Create(*context));
+
+  feature_tracker()->Track(DebugFeatureTracker::kActive);
+
   return true;
 }
 
@@ -625,6 +638,8 @@ bool Debug::SetBreakPoint(Handle<JSFunction> function,
   *source_position = location.statement_position();
   location.SetBreakPoint(break_point_object);
 
+  feature_tracker()->Track(DebugFeatureTracker::kBreakPoint);
+
   // At least one active break point now.
   return debug_info->GetBreakPointCount() > 0;
 }
@@ -666,6 +681,8 @@ bool Debug::SetBreakPointForScript(Handle<Script> script,
       debug_info, ALL_BREAK_LOCATIONS, position, alignment);
   location.SetBreakPoint(break_point_object);
 
+  feature_tracker()->Track(DebugFeatureTracker::kBreakPoint);
+
   position = (alignment == STATEMENT_ALIGNED) ? location.statement_position()
                                               : location.position();
 
@@ -874,6 +891,8 @@ void Debug::PrepareStep(StepAction step_action,
   JavaScriptFrameIterator frames_it(isolate_, id);
   JavaScriptFrame* frame = frames_it.frame();
 
+  feature_tracker()->Track(DebugFeatureTracker::kStepping);
+
   // First of all ensure there is one-shot break points in the top handler
   // if any.
   FloodHandlerWithOneShot();

src/debug/debug.h

@@ -343,6 +343,28 @@ class LockingCommandMessageQueue BASE_EMBEDDED {
 };
 
 
+class DebugFeatureTracker {
+ public:
+  enum Feature {
+    kActive = 1,
+    kBreakPoint = 2,
+    kStepping = 3,
+    kHeapSnapshot = 4,
+    kAllocationTracking = 5,
+    kProfiler = 6,
+    kLiveEdit = 7,
+  };
+
+  explicit DebugFeatureTracker(Isolate* isolate)
+      : isolate_(isolate), bitfield_(0) {}
+  void Track(Feature feature);
+
+ private:
+  Isolate* isolate_;
+  uint32_t bitfield_;
+};
+
+
 // This class contains the debugger support. The main purpose is to handle
 // setting break points in the code.
 //
@@ -508,6 +530,8 @@ class Debug {
 
   StepAction last_step_action() { return thread_local_.last_step_action_; }
 
+  DebugFeatureTracker* feature_tracker() { return &feature_tracker_; }
+
  private:
   explicit Debug(Isolate* isolate);
 
@@ -606,6 +630,9 @@ class Debug {
   // before returning to the DebugBreakCallHelper.
   Address after_break_target_;
 
+  // Used to collect histogram data on debugger feature usage.
+  DebugFeatureTracker feature_tracker_;
+
   // Per-thread data.
   class ThreadLocal {
    public:

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);
 }
 
 

src/profiler/heap-profiler.cc

@@ -5,6 +5,7 @@
 #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"
 
@@ -75,6 +76,10 @@ HeapSnapshot* HeapProfiler::TakeSnapshot(
   }
   ids_->RemoveDeadEntries();
   is_tracking_object_moves_ = true;
+
+  heap()->isolate()->debug()->feature_tracker()->Track(
+      DebugFeatureTracker::kHeapSnapshot);
+
   return result;
 }
 
@@ -86,6 +91,8 @@ void HeapProfiler::StartHeapObjectsTracking(bool track_allocations) {
   if (track_allocations) {
     allocation_tracker_.Reset(new AllocationTracker(ids_.get(), names_.get()));
     heap()->DisableInlineAllocation();
+    heap()->isolate()->debug()->feature_tracker()->Track(
+        DebugFeatureTracker::kAllocationTracking);
   }
 }
 

src/runtime/runtime-liveedit.cc

@@ -229,6 +229,8 @@ RUNTIME_FUNCTION(Runtime_LiveEditCompareStrings) {
   CONVERT_ARG_HANDLE_CHECKED(String, s1, 0);
   CONVERT_ARG_HANDLE_CHECKED(String, s2, 1);
 
+  isolate->debug()->feature_tracker()->Track(DebugFeatureTracker::kLiveEdit);
+
   return *LiveEdit::CompareStrings(s1, s2);
 }